Add example for enter, shells and view-source, update some docs (#4604)

docs/commands/shells.md

@@ -9,3 +9,15 @@ Lists all open shells.
 ## Signature
 
 ```> shells ```
+
+## Examples
+
+Enter a new shell at parent path '..' and show all opened shells
+```shell
+> enter ..; shells
+```
+
+Show currently active shell
+```shell
+> shells | where active == $true
+```