chore(ci): add github action for PR's

.github/workflows/no-pr.yml

@@ -0,0 +1,21 @@
+name: Close pull request
+
+on:
+  pull_request_target:
+    types:
+      - opened
+
+jobs:
+  close-pr:
+    permissions:
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - run: gh pr close "$NUMBER" --comment "$COMMENT"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_REPO: ${{ github.repository }}
+          NUMBER: ${{ github.event.number }}
+          COMMENT: >
+            Thank you for submitting your pull request.
+            Please note that the main repository is located at https://git.naxdy.org/NaxdyOrg/NaxGCC-HW - please submit your pull request there if you would like it to be considered for merging.

README.md

@@ -1,5 +1,17 @@
 # NaxGCC-HW
 
+The main repository is located at [git.naxdy.org](https://git.naxdy.org/NaxdyOrg/NaxGCC-HW). The GitHub mirror exists solely for the sake of discoverability and redundancy.
+
+> **Please do not submit issues or pull requests on GitHub.**
+
+Find the latest releases here: https://git.naxdy.org/NaxdyOrg/NaxGCC-HW/releases
+
+Full documentation is available at [gcc.naxdy.org](https://gcc.naxdy.org/).
+
+Join the NaxGCC matrix chat at [#naxgcc:naxdy.org](https://matrix.to/#/#naxgcc:naxdy.org) to discuss development or ask for help.
+
+---
+
 Seperate repository for the hardware used in the NaxGCC
 
 The NaxGCC board is licensed under CERN Open Hardware Licence Version 2 - Strongly Reciprocal.