ci: verify mmdb file after build

Author: mochaaP

.github/workflows/build.yml

@@ -40,6 +40,14 @@ jobs:
         run: |
           go run .
 
+      - name: Verify mmdb files
+        run: |
+          cd ./output/maxmind || exit 1
+          go install -v github.com/maxmind/mmdbverify@latest
+          for name in $(ls *.mmdb); do
+            $(go env GOPATH)/bin/mmdbverify -file ${name}
+          done
+
       - name: Generate sha256 checksum for mmdb files
         run: |
           cd ./output/maxmind || exit 1