Treat .ts links in statuses as application/typescript

Fixes https://gitlab.com/soapbox-pub/ditto/-/issues/241

src/utils/media.test.ts

@@ -7,6 +7,10 @@ Deno.test('getUrlMediaType', () => {
   assertEquals(getUrlMediaType('https://example.com/index.html'), 'text/html');
   assertEquals(getUrlMediaType('https://example.com/yolo'), undefined);
   assertEquals(getUrlMediaType('https://example.com/'), undefined);
+  assertEquals(
+    getUrlMediaType('https://gitlab.com/soapbox-pub/nostrify/-/blob/main/packages/policies/WoTPolicy.ts'),
+    'application/typescript',
+  );
 });
 
 Deno.test('isPermittedMediaType', () => {

src/utils/media.ts

@@ -1,4 +1,4 @@
-import { typeByExtension } from '@std/media-types';
+import { typeByExtension as _typeByExtension } from '@std/media-types';
 
 /** Get media type of the filename in the URL by its extension, if any. */
 export function getUrlMediaType(url: string): string | undefined {
@@ -22,3 +22,13 @@ export function isPermittedMediaType(mediaType: string, permitted: string[]): bo
   const [baseType, _subType] = mediaType.split('/');
   return permitted.includes(baseType);
 }
+
+/** Custom type-by-extension with overrides. */
+function typeByExtension(ext: string): string | undefined {
+  switch (ext) {
+    case 'ts':
+      return 'application/typescript';
+    default:
+      return _typeByExtension(ext);
+  }
+}