Add link tester to CI (#164)

For this repository, I wrote a small Github Action to check the validity of links.

https://github.com/marketplace/actions/links-check-action

Demo on [my Gitea instance](https://git.zetcraft.ru/serega404/awesome-gitea/actions/runs/19)
Demo on [Github](https://github.com/serega404/awesome-gitea/actions/runs/16038610102/job/45255671331)

Output example:
<img width="1420" alt="image.png" src="attachments/5364cf47-8606-4f2d-bd78-03da442cef8b">

Reviewed-on: https://gitea.com/gitea/awesome-gitea/pulls/164
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Sergey Karmanov <ppoocpel8888@gmail.com>
Co-committed-by: Sergey Karmanov <ppoocpel8888@gmail.com>

.gitea/workflows/testlinks.yml

@@ -0,0 +1,16 @@
+name: Test links
+on:
+  - push
+  - pull_request
+
+jobs:
+  check_urls:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+      - name: Link check action
+        uses: serega404/links-check-action@v0.0.1
+        with:
+          filePath: "README.md"
+          ignoreCodes: "403,418"