Add build timeout

Timeout the build after 15 minutes.

Author: martincostello

.github/workflows/build.yml

@@ -24,6 +24,7 @@ jobs:
   build:
     name: ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
+    timeout-minutes: 15
 
     outputs:
       dotnet-sdk-version: ${{ steps.setup-dotnet.outputs.dotnet-version }}