Add polyfill for making MediaQueryList extend the EventTarget interface

[santialbo]

As discussed in #1069. I separated the implementation as a new polyfill so it can be included independently.
I have several concerns:

• I dind't include the implementation of dispatchEvent. If the implementation is not the one in the matchMedia polyfill there's is no way that I know of accessing the list of listeners.
• I'm not sure the path I chose is the correct. Please let me know if you would put it somewhere else and I'll make the change right away.
• I'm not sure I've got the config.toml right.

[romainmenke]

see : santialbo#1

@JakeChampion To really test event listeners on MediaQueryList I needed to have iframes that are polyfilled.
To achieve this I extended test/polyfills.

In short :

• new endpoint in the test server : iframe.html
• uses createEndpoint so doesn't add more complexity in server.js
• test-iframe.handlebars mirrors test-runner.handlebars but only loads the polyfill javascript and nothing else
• test-runner.handlebars has a <meta> tag to expose the correct URL for the URL to tests.

in tests :

var iframe = document.createElement("iframe");
iframe.src = document.getElementById('test-iframe-src').getAttribute('content');

The result is a same origin iframe with all polyfills applied.

Feel free to shoot this down :)
Maybe there is another way to test this polyfill without modifying the test server?

[JakeChampion]

I don't see another way, I like this approach 👍

[santialbo]

This is now updated with your changes @romainmenke

[JakeChampion]

The current changes in this pull-request would likely be breaking changes due to the removal of two feature names:

• MediaQueryList.prototype.EventTarget
• MediaQueryList.prototype.dispatchEvent

If we wanted to keep this change backwards compatible, we should add those two feature names as aliases to the file polyfills/MediaQueryList/prototype/addEventListener/config.toml

[romainmenke]

@JakeChampion Is it possible you were looking at New changes since you last viewed ?
I removed those two aliases from this PR because the features are not implemented (or not fully).
They were however new additions, not existing aliases on the main branch.

[JakeChampion]

@JakeChampion Is it possible you were looking at New changes since you last viewed ?
I removed those two aliases from this PR because the features are not implemented (or not fully).
They were however new additions, not existing aliases on the main branch.

Yep 🤦 - good work noticing what I did there 😅