feat: proxy font-subset now that we're uploading it.

Uploading in shorebirdtech/_build_engine#175

packages/artifact_proxy/tool/generate_manifest.sh

@@ -77,13 +77,16 @@ artifact_overrides:
 
   # Linux release artifacts
   - flutter_infra_release/flutter/\$engine/linux-x64/artifacts.zip
+  - flutter_infra_release/flutter/\$engine/linux-x64/font-subset.zip
   - flutter_infra_release/flutter/\$engine/linux-x64-release/linux-x64-flutter-gtk.zip
 
   # macOS release artifacts
+  - flutter_infra_release/flutter/\$engine/darwin-x64/font-subset.zip
   - flutter_infra_release/flutter/\$engine/darwin-x64-release/artifacts.zip
   - flutter_infra_release/flutter/\$engine/darwin-x64-release/framework.zip
   - flutter_infra_release/flutter/\$engine/darwin-x64-release/gen_snapshot.zip
 
   # Windows release artifacts
   - flutter_infra_release/flutter/\$engine/windows-x64/artifacts.zip
+  - flutter_infra_release/flutter/\$engine/windows-x64/font-subset.zip
   - flutter_infra_release/flutter/\$engine/windows-x64-release/windows-x64-flutter.zip