docs(material/list): add example of line scenarios with checkbox

Add example of line scenarios with checkbox.

Author: zarend

src/dev-app/list/list-demo.html

@@ -243,6 +243,31 @@ <h2>Line scenarios</h2>
       </mat-list-item>
     </mat-list>
 
+    <mat-selection-list>
+      <mat-list-option>Title</mat-list-option>
+      <mat-list-option lines="2">
+        <span matListItemTitle>Title</span>
+        <span>This is unscoped text content that is supposed to not wrap. The list has only
+        acquired two lines and therefore there is no space for wrapping.</span>
+      </mat-list-option>
+      <mat-list-option lines="3">
+        <span matListItemTitle>Title</span>
+        <span>This is unscoped text content that is supposed to wrap to the third line.
+          The list item acquire spaces for three lines and text should have an ellipsis in the
+          third line upon text overflow.</span>
+      </mat-list-option>
+      <mat-list-option>
+        <span matListItemTitle>Title</span>
+        <span>This is unscoped text content that is supposed to not wrap. The list has only
+        acquired two lines (automatically) and therefore there is no space for wrapping.</span>
+      </mat-list-option>
+      <mat-list-option>
+        <span matListItemTitle>Title</span>
+        <span matListItemLine>Secondary line</span>
+        <span matListItemLine>Tertiary line</span>
+      </mat-list-option>
+    </mat-selection-list>
+
     <button mat-raised-button (click)="showBoxes = !showBoxes">Show item boxes</button>
   </div>