feat(ui): replace Monaco with CodeMirror (#10559)

- Replace the [Monaco Editor](https://microsoft.github.io/monaco-editor/)
with [CodeMirror 6](https://codemirror.net/). This editor is used to
facilitate the 'Add file' and 'Edit file' functionality.
- Rationale:
  - Monaco editor is a great and powerful editor, however for Forgejo's
  purpose it acts more like a small IDE than a code editor and is doing
  too much. In my limited user research the usage of editing files via
  the web UI is largely for small changes that does not need the
  features that Monaco editor provides.
  - Monaco editor has no mobile support, Codemirror is very usable on mobile.
  - Monaco editor pulls in large dependencies (for language support) and
  by replacing it with Codemirror the amount of time that webpack needs
  to build the frontend is reduced by 50% (~30s -> ~15s).
  - The binary of Forgejo (build with `bindata` tag) is reduced by 2MiB.
  - Codemirror is much more lightweight and should be more usable on
  less powerful hardware, most notably the lazy loading is much faster
  as codemirror uses less javascript.
  - Because Codemirror is modular it is much easier to change the
  behavior of the code editor if we wish to.
- Drawbacks:
  - Codemirror is quite modular and as seen in `package.json` and in
  `codeeditor.ts` we have to supply a lot more of its features to have
  feature parity with Monaco editor.
  - Monaco editor has great integrated language support (features that
  an lsp would provide), Codemirror only has such language support to an
  extend.
  - Monaco editor has its famous command palette (known by many as its
  also available in VSCode), this is not available in code mirror.
- Good to note:
  - All features that was added on top of the monaco editor (such as
  dynamically changing language  support depending on the filename)
  still works and the theme is based on the VSCode colors which largely
  resembles the monaco editor.
  - The code editor is still lazy-loaded (this is painfully clear by
  reading how imports are passed around in `codeeditor.ts`).
  - This change was privately tested by a few people, a few bugs were
  found (and fixed) but no major drawbacks were noted for their usage of
  the web editor.
  - There's a "search" button in the top bar, so that search can be used
  on mobile. It is otherwise only accessible via
  <kbd>Ctrl</kbd>+<kbd>f</kbd>.

Co-authored-by: Beowulf <beowulf@beocode.eu>

Co-authored-by: Gusted <postmaster@gusted.xyz>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/10559
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Co-committed-by: Beowulf <beowulf@beocode.eu>

options/locale_next/locale_en-US.json

@@ -248,5 +248,13 @@
 	"admin.auths.oauth2_quota_group_claim_name": "Claim name providing group names for this source to be used for quota management. (Optional)",
 	"admin.auths.oauth2_quota_group_map": "Map claimed groups to quota groups. (Optional - requires claim name above)",
 	"admin.auths.oauth2_quota_group_map_removal": "Remove users from synchronized quota groups if user does not belong to corresponding group.",
+	"editor.search": "Search",
+	"editor.find_previous": "Previous find",
+	"editor.find_next": "Next find",
+	"editor.replace": "Replace",
+	"editor.replace_all": "Replace all",
+	"editor.toggle_case": "Toggle case sensitivity",
+	"editor.toggle_regex": "Toggle using regular expressions",
+	"editor.toggle_whole_word": "Toggle matching whole words",
 	"meta.last_line": "Thank you for translating Forgejo! This line isn't seen by the users but it serves other purposes in the translation management. You can place a fun fact in the translation instead of translating it."
 }