docker-login: add page

pages/common/docker-login.md

@@ -0,0 +1,12 @@
+# docker login
+
+> Log into a docker registry.
+> More information: <https://docs.docker.com/engine/reference/commandline/login/>.
+
+- Log into registry with username and password:
+
+`docker login -u {{username}} -p {{password}} {{server}}`
+
+- Log into registry with password from stdin:
+
+`{{cat path/to/password.txt}} | docker login -u {{username}} --password-stdin`