build: Update main.yml to enable manual running (#77)

Signed-off-by: Richard Beauchamp <[email protected]>

.github/workflows/main.yml

@@ -1,6 +1,7 @@
 name: CI
 
 on:
+  workflow_dispatch:
   push:
     branches: [ main ]
 
@@ -70,4 +71,4 @@ jobs:
         version: ${{ env.NUGET_VERSION }}
         config-name: release-drafter.yml
       env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}