Enable build workflow for pico-3.0 branch

Author: PhrozenByte

.github/workflows/build.yml

@@ -2,7 +2,9 @@ name: Build Pico CMS
 
 on:
     push:
-        branches: [ 'master' ]
+        branches:
+            - 'master'
+            - 'pico-3.0'
         tags: [ 'v*.*.*' ]
     workflow_call: {}