ci: add Gitea Actions workflow for make check (closes #96)

All external references pinned by commit hash:
- actions/checkout@34e114876b (v4)
- actions/setup-go@40f1582b24 (v5)
- golangci-lint@5d1e709b7b (v2.10.1)
- goimports@009367f5c1 (v0.42.0)

.gitea/workflows/check.yml

@@ -10,17 +10,17 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
         with:
           go-version-file: go.mod
 
       - name: Install golangci-lint
-        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.10.1
+        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee # v2.10.1
 
       - name: Install goimports
-        run: go install golang.org/x/tools/cmd/goimports@latest
+        run: go install golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0 # v0.42.0
 
       - name: Run make check
         run: make check