move workflow file to correct path

.gitea/workflows/build-kernel.yaml

@@ -0,0 +1,30 @@
+name: Build Custom Kernel
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build-kernel:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Nix
+        run: |
+          curl -L https://nixos.org/nix/install | sh
+          source ~/.nix-profile/etc/profile.d/nix.sh
+
+      - name: Build custom kernel
+        run: |
+          export NIX_BUILD_CORES=0
+          nix-build '<nixpkgs/nixos>' -A config.system.build.kernel --arg configuration ./custom-kernel.nix
+
+      - name: Upload kernel artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: custom-kernel
+          path: ./result