add manual trigger

Also cut to running on just one version of python

Author: jacalata

.github/workflows/check-coverage.yml

@@ -5,14 +5,15 @@ on:
   pull_request:
     branches:
       - development
+  workflow_dispatch:
 
 jobs:
   build:
     strategy:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ['3']
+        python-version: ['3.12']
 
     runs-on: ${{ matrix.os }}