Make an original event context accessible as [$el] in events

[thisYogesh]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

PR details:
Currently we don't have direct access to the original event context i.e. an element upon which event has been applied. This feature is kind of an alternative for ref but not complete replacement, of course, And I think people would like to use it.

Usage of this feature:

• <div id="item" @click="handler($el)"></div>
• Where $el is the respective element i.e. #item.

[posva]

Thank you for the proposal. I don't think we should add this: the $event holds already the target. If you think this should be added to Vue, you should open an RFC in our rfcs repository

[thisYogesh]

Thanks for your response @posva!
I'm aware of $event and event target, but event target is not always the element upon which event is applied!