Add workflow_dispatch to CI.yml (#217)

So I can just trigger CI manually rather than needing a PR like this to test https://github.com/JuliaBinaryWrappers/GEOS_jll.jl/releases/tag/GEOS-v3.13.1%2B0

Author: visr

.github/workflows/CI.yml

@@ -5,6 +5,7 @@ on:
     branches:
       - master
     tags: '*'
+  workflow_dispatch:
 jobs:
   test:
     name: Julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ github.event_name }}