Prevent SVG shrinking (#25652)

This will prevent the most common cases of SVG shrinking because lack of
space. I evaluated multiple options and this seems to be the one with
the least impact in size and processing cost, so I went with it.

Unfortunately, CSS can not dynamically convert `16` obtained from
`attr()` to `16px`, or else a generic solution for all sizes would have
been possible. But a solution is [in
sight](https://developer.mozilla.org/en-US/docs/Web/CSS/attr#type-or-unit)
with `attr(width px)` but no browser supports it currently.

web_src/css/index.css

@@ -10,6 +10,7 @@
 @import "./modules/navbar.css";
 @import "./modules/toast.css";
 @import "./modules/divider.css";
+@import "./modules/svg.css";
 
 @import "./shared/issuelist.css";
 @import "./shared/milestone.css";