Add alternate legacy browser content

[capilkey]

This PR implements Meteor's built-in legacy browser detection in order to load an alternate minimal client that will render on all devices. I had to duplicate the react-intl initialization because the original implementor imports classes that cause issues. I also couldn't use SCSS because it will use Proxy and it's not possible to polyfill Proxy.

I put in two different messages depending on whether or not the browser is not supported (IE) or an old version of supported browser. I also included a fallback static string for the scenario where the locale can't be loaded.

IE:

Old Chrome:

[antobinary]

Others might have similar questions so let's clear it up:

1. Chromium is not in the list of supported browsers. userAgent does not include 'Chrome' https://developers.whatismybrowser.com/useragents/parse/626626-chromium-windows-webkit
   Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chromium/60.0.3112.78 Safari/537.36

2. Brave, Opera, Yandex seem to have some of these default browsers strings but not Dolphin (from what I see)

3. I guess people will tell us if we restrict the use of their browser. I am not able to find the comment but there was a note from @zhu (I believe) on little tweaks needed to get the client fully running in his browser

[kepstin]

It would be good to have Chromium in the supported list - it's just a build of Chrome from open-source with a few features (drm, flash, google tracking) disabled or off by default. Those features won't affect the HTML5 client. We should use the same required/recommended version for both Chrome and Chromium.
I personally use Chromium on a few of my systems :)

[capilkey]

Chromium falls under the same detection and messaging as Chrome. There's no functional difference between the two.

As for other more obscure browsers, I don't have them so I can't test them. I would guess that they would just try and load the normal application.

As far as I can tell there's no official documentation on how to use this so I'm just working off of the list of browsers in the release notes. https://blog.meteor.com/meteor-1-7-and-the-evergreen-dream-a8c1270b0901

[antobinary]

Does not help for BB10 browser but it seems to work for out of date Chrome/ FF, etc and it does not seem to interfere with up-to-date clients

[zhu]

Our users mainly use the html5 client in webview inside Wechat app.
Here are useragents:
https://developers.whatismybrowser.com/useragents/explore/software_name/wechat/
It seems that brower-detect cannot detect some of them.

I do not have time to upgrade and test the client recently.

[zhu]

PS: camera and mic can not work in this env because the app perms limit. We just use the whiteboard there.

[capilkey]

It should be fine. The browser detection that this is using in Meteor is a blacklist rather than a whitelist so any unknown browsers will get directed to the main application the same as it is now. Because of that the browser-detect usage won't come in to play for other browsers.

[aviavinas]

It worked in my case when i changed the userAgentString:

        WebSettings settings = webView.getSettings();
        settings.setUserAgentString("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.97 Safari/537.36");