Add new aliases

[valtlai]

Adds aliases:

• atom and rss for markup
• webmanifest for json (see Web App Manifest).

[RunDevelopment]

Thank you for making this PR @valtlai!

Could you please clarify what "Atom" is? I only know this Atom and this atom.

It seems that the name atom collides with something, since it doesn’t get added to plugins/show-language/prism-show-language.js (or its minified version) when running gulp. I couldn’t find the reason for this.

Most language ids are just the name of the language in all-lowercase, so Show Language will try to guess the title by capitalizing the id. If that guess is correct, then the id-title pair won't be stored in prism-show-language.js.
If I remember correctly, we guess about 30% correctly, so this decreases the file size quite a bit.

Also, don't worry. If any aliases/ids collide, the tests won't pass.

[valtlai]

Hi, @RunDevelopment!

Could you please clarify what "Atom" is? I only know this Atom and this atom.

It’s Atom feed, like RSS but less known.

Most language ids are just the name of the language in all-lowercase, so Show Language will try to guess the title by capitalizing the id. If that guess is correct, then the id-title pair won't be stored in prism-show-language.js.
If I remember correctly, we guess about 30% correctly, so this decreases the file size quite a bit.

Oh, that’s clever!

[RunDevelopment]

Thanks for the clarification.

One last thing before we merge this: Could you please revert the reordering? The ordering in prism-markup.js is a pure implementation detail and has nothing to do with the order in components.json. Also, I like the older order because it's roughly sorted from most-used to least-used.
I think it's ok if we just append new aliases. (If we created some rule for their ordering then we'd also have to write a test that enforces that rule.)

[RunDevelopment]

Thank you for contributing @valtlai!