refactor(tiptap-extensions): Do not import the full lowlight library.

[erickwilder]

BREAKING CHANGE: CodeBlockHighlight was importing the full lowlight libraries, including all
syntax highlighting definitions from highlight.js. The new behavior changes the signature of
CodeBlockHighlight to accept an object with all syntax highlighting definitions. This means that
now the user of the library MUST import languages themselves and tiptap will no longer
bundle the full highlight.js in itself.

---

Testing:

• Given that you have a working copy from the test repo[1]
• Run npm run build in the test repo and check if the highlight.js library is bundled with it.
• Checkout this branch and run yarn build:packages
• Copy[2] the contents of tiptap-extensions to the test repo:

  cp -R packages/tiptap-extensions /path/to/test/repo/node_modules/tiptap-extensions
  

• Run npm run build again on the rest repo
• You shouldn't see traces of highlight.js anymore.

Expected result:

---

This closes #16

[1] https://github.com/erickwilder/tiptap-treeshaking
[2] I had some issues with npm link and just to be quick I've copied the locally compiled tiptap-extensions over the files installed vie npm install in the test repo.

[erickwilder]

@philippkuehn It would be nice to add the hacktoberfest label in the affected issue (#16, or this PR)😄

Let's make the 1.0.0 roadmap happen! 🍻

[philippkuehn]

Thank you @erickwilder!