chore(reference-menu): add Web Extensions item

[caugner]

Summary

Fixes https://github.com/mdn/yari/issues/5876.

Problem

The old MDN design had a "Browser extensions" item in the "Technologies" menu (see here), but the menus of the new MDN design do not have this menu item anymore.

Solution

Add a "Browser extensions" item to the "References" menu.

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Screenshots

Before

After

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How did you test this change?

• Open http://localhost:3000/en-US/plus locally.

[caugner]

@Rumyra Since the referenced page is still called "Browser Extensions", I have drafted this PR with these information for now:

• Title: Browser Extensions
• Subtitle: Developing extensions for web browsers
• URL: /docs/Mozilla/Add-ons/WebExtensions

[caugner]

Converted to draft, because this requires more discussion.

[caugner]

Closing this, see: https://github.com/mdn/yari/issues/5876#issuecomment-1086057927

[dipikabh]

For the subtitle, how about: "Extensions for web browsers" so that it's parallel in language with other subtitles? Instead of the proposed "Developing extensions for web browsers"

[Rumyra]

The spec all the docs are derived from is 'Web Extensions' and ideally in the future the content will change to reflect this

For the subtitle, how about: "Extensions for web browsers" so that it's parallel in language with other subtitles?

It should reflect the spec, but as I'm just looking into it there's a disparagy between browser vs web - I might change this back...

[dipikabh]

Should "Web Extensions" (new name) come after the "Web Technology" menu?

[Rumyra]

Should "Web Extensions" (new name) come after the "Web Technology" menu?

No - that's an overview page.

My suggestion is good @caugner - let's go with 'Web Extensions' 👍