Add GH Action workflow for nob.

.github/workflows/nob.yml

@@ -0,0 +1,16 @@
+name: nob
+run-name: ${{ github.actor }} is building with nobuild
+on:
+  push:
+  workflow_dispatch:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Build with nob
+      - run: |
+          g++ -std=c++20 -fpermissive -o nob nob.cpp
+          ./nob