Remove bypass and use use glitch-soc's theming system for inert.css

app/javascript/core/inert.js

@@ -0,0 +1,4 @@
+/* Placeholder file to have `inert.scss` compiled by Webpack
+   This is used by the `wicg-inert` polyfill */
+
+import '../styles/inert.scss';

app/javascript/core/theme.yml

@@ -10,6 +10,9 @@ pack:
   embed: embed.js
   error:
   home:
+  inert:
+    filename: inert.js
+    stylesheet: true
   mailer:
     filename: mailer.js
     stylesheet: true