security-checker: add page (#4407)

pages/common/security-checker.md

@@ -0,0 +1,16 @@
+# security-checker
+
+> Check if a PHP application uses dependencies with known security vulnerabilities.
+> More information: <https://github.com/sensiolabs/security-checker>.
+
+- Look for security issues in the project dependencies (based on the composer.lock file in the current folder):
+
+`security-checker security:check`
+
+- Use a specific composer.lock file:
+
+`security-checker security:check {{path/to/composer.lock}}`
+
+- Return results as a JSON object:
+
+`security-checker security:check --format=json`