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/base.css

@@ -16,6 +16,7 @@
   --border-radius: 0.28571429rem;
   --opacity-disabled: 0.55;
   --height-loading: 16rem;
+  --tab-size: 4;
   /* base colors */
   --color-primary: #4183c4;
   --color-primary-contrast: #ffffff;
@@ -230,6 +231,7 @@ h6 {
 body {
   color: var(--color-text);
   background-color: var(--color-body);
+  tab-size: var(--tab-size);
   overflow-y: auto;
   display: flex;
   flex-direction: column;