mr: add page (#1785)

pages/common/mr.md

@@ -0,0 +1,19 @@
+# mr
+
+> Myrepos manages all your version control repositories at once.
+
+- Register a repository:
+
+`mr register`
+
+- Update repositories in 5 concurent jobs:
+
+`mr -j{{5}} update`
+
+- Print the status of all repositories:
+
+`mr status`
+
+- Checkout all repositories to the latest version:
+
+`mr checkout`