Set a default shell for all jobs

Setting the shell to 'bash' turns on -e and -o pipefail, both of which are very
desirable to have.

actions/runner-images#4459 (comment)

Author: stefanhaller

.github/workflows/release.yml

@@ -22,6 +22,10 @@ on:
         required: true
         default: false
 
+defaults:
+  run:
+    shell: bash
+
 jobs:
   check-and-release:
     runs-on: ubuntu-latest