Improve workflow event filters.

- Fix primary branch to `master`.
- Filter zizmor checks to `.github` tree changes.
- Use same style in workflow files.

Author: davidlehn

.github/workflows/main.yaml

@@ -1,10 +1,12 @@
 name: Main CI
 
 on:
-  pull_request:
   push:
     branches:
-      - main
+      - 'master'
+  pull_request:
+    branches:
+      - '**'
 
 permissions: {}
 

.github/workflows/zizmor.yaml

@@ -2,9 +2,15 @@ name: GitHub Actions Security Analysis with zizmor
 
 on:
   push:
-    branches: ["main"]
+    branches:
+      - 'master'
+    paths:
+      - '.github/**'
   pull_request:
-    branches: ["**"]
+    branches:
+      - '**'
+    paths:
+      - '.github/**'
 
 permissions: {}