Formalize process for browser checks and create relevant files
The following discussion from gitlab-ce!24017 should be addressed:
- [ ] @pslaughter started a [discussion](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24017#note_131781883): (+3 comments)
> @kushalpandya, thanks for this! I think it is a good idea to capture this on the DOM. However, I'm concerned about our code being peppered with browser checks:
>
> ```javascript
> function initializingWombats() {
> if (isChrome || isFirefox) {
> // ...
> }
>
> if (!isIE11 && !isEdge) {
> // ...
> }
> }
> ```
>
> What if we strictly limit these browser checks in a single `features.js`?
>
> ```javascript
> const { isIe, isEdge, isChrome, isFirefox } = gl.client;
>
> export const emojisLookGood = () => !isIe && !isEdge;
> export const tooltipsLookGood = () => isChrome || isFirefox;
> // ...
> ```
>
> WDYT?
/cc @kushalpandya @andr3
issue