feat(SearchEngine): Add Gitlab instances

[Syndlex]

So I added Gitlab as a search engine.

It also contains the code for custome Gitlab instances. The problem is that I could not get optional_permissions working with custom URLs added by the Settings UI. Maybe someone with more knowledge about browser extensions can get it to work.

I love this extension and would love to use the workflow on a company gitlab.

[infokiller]

Thanks for the PR! I'll add a few comments to the PR, but A few general ones:

• Remove unrelated formatting changes
• Fix formatting issues (see CodeFactor report) and verify yarn run check has no errors
• Add an entry to the CHANGELOG

[infokiller]

I still see some unrelated formatting changes and incorrect formatting? does yarn check pass?

[lgtm-com[bot]]

This pull request introduces 1 alert when merging 5755e8e464c4a1d9ce19180f142f5fd4e1a9c0a6 into 8d99324c9a144d2774d8d04a2234092e997a855e - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

[Syndlex]

I divided up the custom instance and the normal instance.

Hope this is ok. There is no other way to implement websites on runtime.

[lgtm-com[bot]]

This pull request introduces 1 alert when merging 66e011c77ebe1d7bcc9bfa9e6346140c41536347 into 8d99324c9a144d2774d8d04a2234092e997a855e - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

[infokiller]

I divided up the custom instance and the normal instance.

Hope this is ok. There is no other way to implement websites on runtime.

Yes, this is fine

[infokiller]

Just to let you know that I haven't forgotten about this PR, I just want to test it manually before I merge it, will do it "soon"

[infokiller]

@Syndlex I merged the changes locally, fixed some conflicts and issues, and added regex validation. I accidentally closed this PR because I pushed the master branch to your fork. Let's continue in #525