feat(workflows): Add a PR config build

.forgejo/workflows/eval.yaml

@@ -0,0 +1,26 @@
+name: build configuration
+on:
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build_configs:
+    runs-on: debian-latest
+    steps:
+      - name: Install applications
+        run: apt-get update && apt-get install sudo
+
+      - uses: actions/checkout@v3
+
+      - uses: https://github.com/cachix/install-nix-action@v22
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - name: Update dependencies and open PR if necessary
+        run: |
+          # Enter the shell
+          nix-shell
+
+          # Build the configurations
+          colmena build