Also run the build when pushing tags

Author: robbert-vdh

.github/workflows/build.yml

@@ -4,6 +4,10 @@ on:
   push:
     branches:
       - master
+    tags:
+      # Run when pushing version tags, since otherwise it's impossible to
+      # restart a successful build after pushing a tag
+      - '*.*.*'
   pull_request:
     branches:
       - master