Cancel CI workflow if new changes are pushed (#175)

Signed-off-by: Andrew Helwer <[email protected]>

Author: ahelwer

.github/workflows/ci.yml

@@ -4,6 +4,9 @@ on:
     branches: [main]
   push:
     branches: [main]
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 jobs:
     test:
         name: Build & Test