config: add --add-data to bundle git-filter-repo source in PyInstaller binary

PyInstaller frozen binaries need the source .py file bundled as data so
git-filter-repo's print_my_version() can locate it at runtime on macOS.

Author: cowwoc

.github/workflows/build-git-filter-repo.yml

@@ -58,6 +58,7 @@ jobs:
           pyinstaller \
             --onefile \
             --name git-filter-repo \
+            --add-data "git-filter-repo:." \
             git-filter-repo
           ls -lh dist/git-filter-repo