Updated: using katex.min.css from node_modules folder, fixes #252, #349

[upupming]

This pull request changes the katex.min.css source from the /media folder to node_modules folder. It fixes #252 #349. I just compared your code with Markdown+Math and find this solution.

After I delete the CSS file under the /media folder. I found there are some changes we need to make to make update katex and other dependencies much easier:

1. Delete all copied files from other packages such as fonts folder, highlight.css, etc. These files are all from npm packages, we should use the files under the node_modules folder to make update them easier.

2. Make @neilsustc/markdown-it-katex accept an katex object like this(copied from Markdown+Math):

   const kt = require('katex'),
         tm = require('markdown-it-texmath').use(kt);

   In this way, we don't need to worry about katex version and update@neilsustc/markdown-it-katex every time when katex releases a new version.

If you agree with me, I will open another PR for this improment~

[yzhang-gh]

Well done! Thanks a lot 👍

---

For point 1, I agree with you. But be careful. The highlight.css seems to be used for code block syntax highlight, which is not related to math.

And for point 2, I would rather keep what it is now for simplicity. katex doesn't update very frequently. So that is not a big problem.

[upupming]

Thanks for you quick response!

By the way, are these font files used? I don't see any code deal with them 😅

[yzhang-gh]

These fonts were referenced by the local katex.min.css but not needed now. I have merged your PRs in. Thank you.