Point Gitea Actions at git.keligrubb.com action mirrors. (#10)

Use self-hosted mirrors for checkout, setup-node, upload-artifact, and
download-artifact. Pin upload/download to v3 so artifact uploads work on
runners that do not support @actions/artifact v2 (GHES-style); set
download path to the workspace root for the release upload script.

Reviewed-on: #10
Co-authored-by: keligrubb <keligrubb324@gmail.com>
Co-committed-by: keligrubb <keligrubb324@gmail.com>

.gitea/workflows/pr.yml

@@ -9,10 +9,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: https://github.com/actions/checkout@v6
+        uses: https://git.keligrubb.com/actions/checkout@v6
 
       - name: Setup Node
-        uses: https://github.com/actions/setup-node@v6
+        uses: https://git.keligrubb.com/actions/setup-node@v6
         with:
           node-version: "24"
           cache: "npm"
@@ -28,10 +28,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: https://github.com/actions/checkout@v6
+        uses: https://git.keligrubb.com/actions/checkout@v6
 
       - name: Setup Node
-        uses: https://github.com/actions/setup-node@v6
+        uses: https://git.keligrubb.com/actions/setup-node@v6
         with:
           node-version: "24"
           cache: "npm"