feat(eslint): add compat eslint plugin

[ismay]

This adds https://www.npmjs.com/package/eslint-plugin-compat. This plugin checks the js APIs you're using against your browserslist. It'll warn you when you're using js APIs that aren't supported by your target audience.

As long as we're sticking to stable browser features, and not polyfilling with babel to features that haven't shipped with browsers yet, this is a useful plugin to have (and even if we do it can be useful, just means that we need to define the polyfills we ship).

[HendrikThePendric]

Seems like another good addition 👍

[ismay]

I've changed the approach here slightly. The recommended preset of this plugin sets all violations to errors, and since our browserslist includes opera mini, most our codebases will fail linting as that browser doesn't support promises:

We could remove opera mini from our browserslist if we don't support it, and otherwise we should ship a promise polyfill. Until then, I'll leave this rule on warn. Once we've decided what we want to do about the above, we could move the rule to error (and potentially configure the plugin so it knows we're shipping a promise polyfill).

[amcgee]

Nice to have confidence in browser compatibility!

We should probably exclude Opera Mini, otherwise we will definitely need the polyfill

[stale]

Hi!

Due to a lack of activity on this issue over time (180 days) it seems to be stale. If still relevant, please provide information that moves it forward, e.g. additional information, a pull request with suggested changes, or a reason to keep it open.

Any activity will keep it open, otherwise it will be closed automatically in 30 days. Thanks! 🤖

[stale]

Automatically closing due to lack of activity. 🤖