update login docs, add step by step information

docs/appbase/login.md

 # login
 
+login command allows you to login into `abc`. 
+
+Here are a few examples -- 
+
 ```sh
+abc login --help
+# view login help
+
 abc login
 # returns current user information
 
@@ -11,3 +18,6 @@ abc login github
 # login with github
 ```
 
+Once you start login into google or github, you will be asked to authenticate `abc` with your google/github account if it isn't already done.
+Then you will be redirected to a page with your Auth token. 
+You will have to paste the token in the command-line window to be authenticated.