dexter: add page (#3040)

pages/common/dexter.md

@@ -0,0 +1,12 @@
+# dexter
+
+> Tool for authenticating the kubectl users with OpenId Connect.
+> Homepage: <https://github.com/gini/dexter>.
+
+- Create and authenticate a user with Google OIDC:
+
+`dexter auth -i {{client-id}} -s {{client-secret}}`
+
+- Override the default kube config location:
+
+`dexter auth -i {{client-id}} -s {{client-secret}} --kube-config {{sample/config}}`