skip PR live build on non-plugin changes (#45891)

Co-authored-by: Ron Rennick <ronald.rennick@automattic.com>

.github/workflows/pr-build-live-branch.yml

@@ -1,8 +1,14 @@
-name: Build Live Branch
+name: Build PR Live Branch
 on:
     pull_request:
         paths-ignore:
+            - '.github/**'
+            - 'docs/**'
+            - 'packages/php/**'
+            - 'tools/**'
             - '**/changelog/**'
+            - '**/tests/**'
+            - '**/*.md'
 
 concurrency:
     # Cancel concurrent jobs on pull_request but not push, by including the run_id in the concurrency group for the latter.