add check workflow and update readme

.github/workflows/check.yaml

@@ -0,0 +1,23 @@
+on:
+  push:
+    branches:
+      - master
+      - prod
+jobs:
+  check:
+    name: Check Flake outputs
+    permissions:
+      contents: read
+    runs-on: ubuntu-latest
+    outputs:
+      flake-check-stderr: ${{ steps.flake-check.outputs.OUT }}
+    steps:
+      - name: Checkout Repo
+        id: checkout
+        uses: actions/checkout@v3
+      - name: Install Nix
+        id: install-nix
+        uses: cachix/install-nix-action@v30
+      - name: Run Flake Check
+        id: flake-check
+        run: nix flake check

README.md

@@ -29,7 +29,7 @@ Secrets are managed with sops-nix. The yubikey is involved in this process. I ha
 
 ## Deployment
 
-Most machines have been deployed with nixos-anywhere. Some were installed with custom generated ISO images. I am no longer using this workflow. For my business, I have built a netboot derivation that helps to quickly install hosts. This is great if you have a lot of hosts to install. I may make those configuration modules available here in the future. Keep an eye out for an article about this workflow on [website](https://m32.io)
+Most machines have been deployed with nixos-anywhere. Some were installed with custom generated ISO images. I am no longer using this workflow. For my business, I have built a netboot derivation that helps to quickly install hosts. This is great if you have a lot of hosts to install. I may make those configuration modules available here in the future. Keep an eye out for an article about this workflow on [my website](https://m32.io)
 
 In general, I build the system closures locally when hacking on this config. That means working with the `nixos-rebuild` development loop. Some features I test with the `nixos-rebuild build-vm` functionality.