gixy: add page (#3190)

pages/common/gixy.md

@@ -0,0 +1,20 @@
+# gixy
+
+> Analyze nginx configuration files.
+> More information: <https://github.com/yandex/gixy>.
+
+- Analyze nginx configuration (default path: /etc/nginx/nginx.conf):
+
+`gixy`
+
+- Analyze nginx configuration but skip specific tests:
+
+`gixy --skips {{http_splitting}}`
+
+- Analyze nginx configuration with the specific severity level:
+
+`gixy {{-l|-ll|-lll}}`
+
+- Analyze nginx configuration files on the specific path:
+
+`gixy {{path/to/configuration_file_1}} {{path/to/configuration_file_2}}`