KaTeX integration with CSS + fix LaTeX processing with blockquotes

[allozaur]

Changes according to ggml-org#16508 (comment).

Additionally applied a fix for an issue i met along the way with the blockquotes:

BEFORE	AFTER

[allozaur]

Yep, I think this is it @srogmann, but if you got any remarks lemme know! Otherwise let's merge it to your branch and move forward with merging the LaTeX/KaTeX improvements to the master branch!

[allozaur]

@srogmann just realized i've merged a lot of commits from the master branch in the main repo, so i think that you could either rebase or merge it to yours as well and then the diff should become clean again in this PR.

[srogmann]

@allozaur Thanks! I transferred the two commits via cherry-picking.

The future will demand changes, but the present is content:

Deprecation Warning [import]: Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.

More info and automated migrator: https://sass-lang.com/d/import

   ╷
17 │ @import 'katex/src/styles/katex.scss';
   │         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   ╵
    src/styles/katex-custom.scss 17:9  root stylesheet

Deprecation Warning [import]: Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.

$ npm list|grep sass
├── [email protected]

.woff2-only in index.html and we got rid of the brittle regex :-):

$ zcat ../public/index.html.gz |cut -b1-60|grep -A4 "@font-face"|egrep "font-family|src: url"|head
  font-family: "KaTeX_AMS";
  src: url("data:font/woff2;base64,d09GMgABAAAAAG2sAA4AAAAA+
  font-family: "KaTeX_Caligraphic";
  src: url("data:font/woff2;base64,d09GMgABAAAAABsAAA4AAAAAM
  font-family: "KaTeX_Caligraphic";
  src: url("data:font/woff2;base64,d09GMgABAAAAABr8AA4AAAAAM
  font-family: "KaTeX_Fraktur";
  src: url("data:font/woff2;base64,d09GMgABAAAAACxUAA4AAAAAT
  font-family: "KaTeX_Fraktur";
  src: url("data:font/woff2;base64,d09GMgABAAAAACw0AA4AAAAAT

[allozaur]

The future will demand changes, but the present is content:

Deprecation Warning [import]: Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.



More info and automated migrator: https://sass-lang.com/d/import



   ╷

17 │ @import 'katex/src/styles/katex.scss';

   │         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   ╵

    src/styles/katex-custom.scss 17:9  root stylesheet



Deprecation Warning [import]: Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.

Yes, of course I saw that. There's a comment about the deprecated @import usage added. Generally this would have to be addressed in the KaTeX scss files, but for this particular change this will be sufficient. I'll see how this gets addressed in the near future and decide how to proceed further.