Start signing JSON v3 cask file

This is now getting generated by the main brew repo after my PR
got merged in and this PR is a follow-up to make sure to sign it.

The next step after this will be to build out the loader code.

- Homebrew/brew#16798

Author: apainintheneck

.github/workflows/scheduled.yml

@@ -41,7 +41,7 @@ jobs:
           HOMEBREW_DEVELOPER: 1
 
       - name: Archive data
-        run: tar czvf data-cask.tar.gz _data/cask/ api/cask/ api/cask-source/ api/cask_tap_migrations.json cask/
+        run: tar czvf data-cask.tar.gz _data/cask/ api/cask/ api/cask-source/ api/cask_tap_migrations.json cask/ api/internal/v3/homebrew-cask.json
 
       - uses: actions/upload-artifact@v3
         with:

script/sign-json.rb

@@ -18,6 +18,7 @@
   ROOT/"_site/api/formula_tap_migrations.json",
   ROOT/"_site/api/cask_tap_migrations.json",
   ROOT/"_site/api/internal/v3/homebrew-core.json",
+  ROOT/"_site/api/internal/v3/homebrew-cask.json",
 ].each do |path|
   data_string = path.read