build linux-arm in Nix Flake GitHub Action

https://docs.github.com/en/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners

Author: peterbecich

.github/workflows/nix-flake.yml

@@ -13,6 +13,7 @@ jobs:
       matrix:
         os:
         - ubuntu-latest
+        - ubuntu-24.04-arm
         - macos-latest
     name: Nix on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}