Improve Rich Text typography (#11157)

* Replace @fontsource/noto-serif with local Noto Serif fonts
* Make more use of CSS variables in theme
* Make sure the chosen font is used for monospace
* Increase the weight of section headings
* Set link colours
* Rename variable to --source-font-family

GitOrigin-RevId: e14856a619829e075e71bf2df9b799fe0b45acea

services/web/package.json

@@ -81,7 +81,6 @@
     "@codemirror/view": "^6.7.1",
     "@contentful/rich-text-html-renderer": "^16.0.2",
     "@contentful/rich-text-types": "^16.0.2",
-    "@fontsource/noto-serif": "^4.5.11",
     "@google-cloud/bigquery": "^6.0.1",
     "@lezer/common": "^1.0.2",
     "@lezer/highlight": "^1.1.3",