Move fomantic and jQuery to main webpack bundle (#11997)

This saves around 3 MB binary size by not including useless fomantic
files in the build. Also, this allows us to move jQuery into the main
bundle as well which eliminates a few HTTP requests.

Also included are webpack config changes:

- split less and css loaders to speed up compliation
- enable css sourcemaps
- switch css minfier plugin to cssnano-webpack-plugin which works better
  for sourcemaps than the previous plugin

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

semantic.json

@@ -9,12 +9,12 @@
       "themes": "src/themes/"
     },
     "output": {
-      "packaged": "../../public/fomantic/",
-      "uncompressed": "../../public/fomantic/components/",
-      "compressed": "../../public/fomantic/components/",
-      "themes": "../../public/fomantic/themes/"
+      "packaged": "../../web_src/fomantic/build/",
+      "uncompressed": "../../web_src/fomantic/build/components/",
+      "compressed": "../../web_src/fomantic/build/components/",
+      "themes": "../../web_src/fomantic/build/themes/"
     },
-    "clean": "../../public/fomantic/"
+    "clean": "../../web_src/fomantic/build/"
   },
   "permission": false,
   "autoInstall": false,