feat: support C3 language highlighting in file editor (#11241)

See https://codeberg.org/Codeberg/Community/issues/2371#issuecomment-10520506
Closes: Codeberg/Community#2371

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11241
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Robert Wolff <mahlzahn@posteo.de>
Co-committed-by: Robert Wolff <mahlzahn@posteo.de>

Author: mahlzahn

web_src/js/features/codemirror-lang.ts

@@ -9,6 +9,13 @@ export function languages(codemirrorLanguage: CodeMirrorLanguage): LanguageDescr
         return (await import('@codemirror/lang-cpp')).cpp();
       },
     }),
+    codemirrorLanguage.LanguageDescription.of({
+      name: 'C3',
+      extensions: ['c3'],
+      async load() {
+        return (await import('@codemirror/lang-cpp')).cpp();
+      },
+    }),
     codemirrorLanguage.LanguageDescription.of({
       name: 'C++',
       alias: ['cpp'],