Call prism before-tokenize and after-tokenize hooks

[manuelpuyol]

Closes #104
Based on https://github.com/PrismJS/prism/blob/022f90a0bf8ac7e40373d1b783354715b0a1020f/prism.js#L606-L616

With this change, users with custom languages can also provide a custom version of Prism to make languages such as ERB to work with <Highlight>

[kitten]

Before reviewing this with white space changes ignored (alas, I don't think we added an editorconfig file to this repo) I'll see if I can carve out some time to see which change is interfering here, but it'd be great to get the commits amended to not change the white space formatting here 😅 it's fine for a separate commit if we do need to normalise them but as a whole it'd be a bit of a problem if a commit for a PR gives us confusing diff's outside of or inside of GitHub in the future 💙

[manuelpuyol]

Hi @kitten thanks for the feedback!
Those white space changes are caused by the pre-commit hook, prettier updates the line ending my files.
Maybe we could run yarn format in the master branch and commit the result? It looks like some files need formatting:

[manuelpuyol]

#106 PR for prettier format!

[kitten]

Alright, a rebase may sort this then 👍

[manuelpuyol]

One more formatting issue before fixing changes here #107 😄

[manuelpuyol]

@kitten diff is now clean!