docs: add name flag to commands in schematic guide (#11283)

Author: AmmarHasan

guides/schematics.md

@@ -35,21 +35,21 @@ a toolbar with the app name and the side nav responsive based on Material
 breakpoints.
 
 ```
-ng generate @angular/material:material-nav
+ng generate @angular/material:material-nav --name <component-name>
 ```
 
 ### Dashboard Schematic
 The dashboard schematic will create a new component that contains
 a dynamic grid list of cards.
 
 ```
-ng generate @angular/material:material-dashboard
+ng generate @angular/material:material-dashboard --name <component-name>
 ```
 
 ### Table Schematic
 The table schematic will create a new table component pre-configured
 with a datasource for sorting and pagination.
 
 ```
-ng generate @angular/material:material-table
+ng generate @angular/material:material-table --name <component-name>
 ```