loadLanguages() should work with aliases

[Golmote]

The loadLanguages() function defined in components/index.js should resolve aliases.

loadLanguages('js');

[mAAdhaTTah]

We could limit the complexity a bit if we broke this into two steps:

1. Generate a list of languages to load based on a provided list of languages and reorder them to ensure peer dependencies are loaded first.
2. Load the languages.

I suggest this because I built something like step 1 into the babel plugin but it doesn't currently handle peerDependencies or aliases. Step 2 in the babel plugin injects the dependencies into the AST. If we extracted that out to a common function, I could offload that logic to prism itself and share it between loadLanguages and the babel plgin.

[mAAdhaTTah]

Also, I think implementing that logic would be easier if the aliases were keyed in components.js, so we would add "js": { "alias": "javascript" } and then we know to go look at "javascript": { ... } for details.

[Golmote]

You're very welcome to start a PR if you want 😉