Enable repository_dispatch for version tagging

Added repository_dispatch event to trigger workflow on new version tags.

Author: briantoby

.github/workflows/matrix_g2main-test.yml

@@ -8,16 +8,15 @@ permissions:
 
 on:
   workflow_dispatch:   # nice for debugging
-  
+  repository_dispatch:
+    types: [new-version-tag]  # Launch when a new version is created  
   push:
     branches: [ "main" ]
     paths:                  # want this to run only when files relevant to
                             # package build change
       - install/gitstrap.py
       - install/GSAS2main/*
       - .github/workflows/*g2main-test.yml
-      
-  #repository_dispatch: # TODO: launch from GSASII repo via Web API
 
 jobs:
   version-matrix: