Update Windows build workflow for branch handling

.github/workflows/windows-build.yml

@@ -1,12 +1,13 @@
 name: Windows Build
 
 on:
-  push:
-    branches:
-      - master
+  # If you want to prove GitHub is seeing this workflow, don't restrict branches here.
+  push: {}
   pull_request:
     branches:
       - master
+      - main
+  workflow_dispatch: {}
 
 jobs:
   windows_build:
@@ -36,7 +37,7 @@ jobs:
       - name: Setup MSYS2 (for GTK build fallback)
         uses: msys2/setup-msys2@v2
         with:
-          msys2-location: C:\tools\msys64
+          msys2-location: "C:\\tools\\msys64"
           update: true
           install: >-
             base-devel