Update sphinx-dev.yml to enable manual run

Author: AnnaBobasheva

.github/workflows/sphinx-dev.yml

@@ -4,6 +4,12 @@ on:
   push:
     branches:
       - "develop"
+  workflow_dispatch:
+    inputs:
+      reason:
+        description: 'Reason for manual trigger'
+        required: false
+        default: 'Manual build requested'
 
 permissions:
   contents: write