Deprecate @master

Author: SaschaMann

action.yml

@@ -17,6 +17,11 @@ inputs:
 runs:
   using: 'composite'
   steps:
+  - name: 'DEPRECATION WARNING: julia-actions/julia-buildpkg@master will no longer receive updates and will start to error in the future. Please use version tags like julia-actions/julia-buildpkg@v1 or commit SHAs in your workflows!'
+    run: |
+      echo "::warning title=DEPRECATION WARNING::julia-actions/julia-buildpkg@master will no longer receive updates and will start to error in the future. Please use version tags like julia-actions/julia-buildpkg@v1 or commit SHAs in your workflows!"
+      echo "# :warning: DEPRECATION WARNING :warning: julia-actions/julia-buildpkg@master will no longer receive updates and will start to error in the future. Please use version tags like julia-actions/julia-buildpkg@v1 or commit SHAs in your workflows!" >> $GITHUB_STEP_SUMMARY
+    shell: bash
   - name: Set and export registry flavor preference
     run: echo "JULIA_PKG_SERVER_REGISTRY_PREFERENCE=${JULIA_PKG_SERVER_REGISTRY_PREFERENCE:-eager}" >> ${GITHUB_ENV}
     shell: bash