feat: add gitea actions workflow

.gitea/workflows/build.yml

@@ -0,0 +1,12 @@
+name: "Test"
+on:  [push]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - run: apt install sudo -y
+      - uses: https://github.com/cachix/install-nix-action@v20
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable-small
+      - run: nix  build