Replace Fomantic reset module with our own (#24948)

Replace the `reset` module with a modern version based on
[modern-normalize](https://github.com/sindresorhus/modern-normalize).
The only things I removed from that module are the `font-family` rules
we don't need. Otherwise, it's similar to Fomantic's reset, but with the
legacy IE stuff removed.

I documented every change done to the module.

Also this introduces a new `--tab-size` variable but it has no real
effect on code yet.

web_src/css/index.css

@@ -1,3 +1,4 @@
+@import "./modules/normalize.css";
 @import "./modules/animations.css";
 @import "./modules/tippy.css";
 @import "./modules/modal.css";