Enable testbuilds on main

Signed-off-by: Nick Slowinski <nick@nick-slowinski.de>

.forgejo/workflows/build.yaml

@@ -1,7 +1,7 @@
 name: Build website
 on:
   push:
-    branches-ignore:
+    branches:
       - main
   pull_request:
     types: [opened, synchronize, reopened]