Update @symfony/webpack-encore to the latest version 🚀 (#3)

## The dependency [@symfony/webpack-encore](https://github.com/symfony/webpack-encore) was updated from `0.21.1` to `0.22.4`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

---

<details>
<summary>Release Notes for v0.22.4 - Fixing Vue + Typescript bug & other minor things</summary>

<p>Yes! A new release - but just some minor fixes.</p>
<p>To upgrade: <code>yarn upgrade</code></p>
<p>Changes: <a href="https://urls.greenkeeper.io/symfony/webpack-encore/compare/v0.22.3...v0.22.4">v0.22.3..v0.22.4</a></p>
<p>Documentation: <a href="http://symfony.com/doc/current/frontend.html" rel="nofollow">http://symfony.com/doc/current/frontend.html</a></p>
<p>Highlights:</p>
<ul>
<li><a class="issue-link js-issue-link" data-error-text="Failed to load issue title" data-id="395514756" data-permission-text="Issue title is private" data-url="symfony/webpack-encore#483" data-hovercard-type="pull_request" data-hovercard-url="/symfony/webpack-encore/pull/483/hovercard" href="https://urls.greenkeeper.io/symfony/webpack-encore/pull/483">#483</a> Add new methods <code>isDev()</code> and <code>isDevServer()</code> - thanks to <a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=2103975" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://urls.greenkeeper.io/Kocal">@Kocal</a></li>
<li><a class="issue-link js-issue-link" data-error-text="Failed to load issue title" data-id="395926749" data-permission-text="Issue title is private" data-url="symfony/webpack-encore#484" data-hovercard-type="pull_request" data-hovercard-url="/symfony/webpack-encore/pull/484/hovercard" href="https://urls.greenkeeper.io/symfony/webpack-encore/pull/484">#484</a> Allow to import .vue files when using TypeScript - thanks to <a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=850046" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://urls.greenkeeper.io/Lyrkan">@Lyrkan</a></li>
<li><a class="issue-link js-issue-link" data-error-text="Failed to load issue title" data-id="395930289" data-permission-text="Issue title is private" data-url="symfony/webpack-encore#485" data-hovercard-type="pull_request" data-hovercard-url="/symfony/webpack-encore/pull/485/hovercard" href="https://urls.greenkeeper.io/symfony/webpack-encore/pull/485">#485</a> Fix small mistakes in shared-entry-concat-plugin.js and validator.js - thanks to <a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=850046" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://urls.greenkeeper.io/Lyrkan">@Lyrkan</a></li>
</ul>
</details>

<details>
<summary>Commits</summary>
<p>The new version differs by 32 commits.</p>
<ul>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/70f47f6795af73e66362080f4668e00b1e048df0"><code>70f47f6</code></a> <code>Tagging 0.22.4</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/a5191f5bf7e7cc146cf6acb3275dbb278db6d64b"><code>a5191f5</code></a> <code>bug #484 Allow to import .vue files when using TypeScript (Lyrkan)</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/8f4178335c489926d548ae0f39a9eb4042276429"><code>8f41783</code></a> <code>minor #485 Fix small mistakes in shared-entry-concat-plugin.js and validator.js (Lyrkan)</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/2d1d6d6e89fef7dc1dc4cb8211f514dc0ef44f01"><code>2d1d6d6</code></a> <code>feature #483 Add new methods <code>isDev()</code> and <code>isDevServer()</code> (Kocal)</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/bf6fb63612056be37e9fdbb6d9f779b897237db3"><code>bf6fb63</code></a> <code>Tagging 0.22.3</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/828788c1a311803c66041fd71ee8c4f41dbe4e93"><code>828788c</code></a> <code>Fix some issues in shared-entry-concat-plugin.js and validator.js</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/8bbc3f642c304536cdeeb78d6fc44393b165b256"><code>8bbc3f6</code></a> <code>Allow to import .vue files when using TypeScript</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/30f410eedc553b41a070132bf5a1091966fe4c48"><code>30f410e</code></a> <code>bug #481 Upgrade webpack-dev-server (cilefen)</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/b428df53e5753ec0a69ed4fbf755c9fc3abfabb7"><code>b428df5</code></a> <code>Fix outdated hashes in one of the copyFiles functional tests</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/c702533f998d9cbeefec20a0005a7335a7232648"><code>c702533</code></a> <code>Add new methods <code>isDev()</code> and <code>isDevServer()</code></code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/3e132176805742c740103a25df1d5c0e7ad70133"><code>3e13217</code></a> <code>Upgrade webpack-dev-server</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/b5750b2fb09053687bcaca59b27a79a8396d304b"><code>b5750b2</code></a> <code>bug #456 Display a warning when calling "copyFiles" with an invalid path (Lyrkan)</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/366f32c0fd366285b339700446c71476f6d048ef"><code>366f32c</code></a> <code>Tagging 0.22.2</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/4b90883f3b4df84f1eaee75349f845d17bba6bc8"><code>4b90883</code></a> <code>bug #463 Using contenthash instead of chunkhash (weaverryan)</code></li>
<li><a href="https://urls.greenkeeper.io/symfony/webpack-encore/commit/3797cba610db5adc0e6127e68bbee02dccb9be3a"><code>3797cba</code></a> <code>Using contenthash instead of chunkhash</code></li>
</ul>
<p>There are 32 commits in total.</p>
<p>See the <a href="https://urls.greenkeeper.io/symfony/webpack-encore/compare/2a73fbc805af70c2e406dc7a62b44a581c71868f...70f47f6795af73e66362080f4668e00b1e048df0">full diff</a></p>
</details>

<details>
  <summary>FAQ and help</summary>

  There is a collection of [frequently asked questions](https://greenkeeper.io/faq.html). If those don’t help, you can always [ask the humans behind Greenkeeper](https://github.com/greenkeeperio/greenkeeper/issues/new).
</details>

---


Your [Greenkeeper](https://greenkeeper.io) bot 🌴