fix(card): add camel-cased selectors to content projection (#6818)

Fixes the camel-cased selectors for `mdCardTitle` and `mdCardSubtitle` not being added to the content projection selector.

Fixes #6816.

Author: crisbeto

src/lib/card/card-header.html

@@ -1,6 +1,8 @@
 <ng-content select="[mat-card-avatar], [matCardAvatar]"></ng-content>
 <div class="mat-card-header-text">
-  <ng-content select="mat-card-title, mat-card-subtitle, [mat-card-title], [mat-card-subtitle]">
-  </ng-content>
+  <ng-content
+      select="mat-card-title, mat-card-subtitle,
+      [mat-card-title], [mat-card-subtitle],
+      [matCardTitle], [matCardSubtitle]"></ng-content>
 </div>
 <ng-content></ng-content>

src/lib/card/card-title-group.html

@@ -1,6 +1,8 @@
 <div>
-  <ng-content select="mat-card-title, mat-card-subtitle, [mat-card-title], [mat-card-subtitle]">
-  </ng-content>
+  <ng-content
+      select="mat-card-title, mat-card-subtitle,
+      [mat-card-title], [mat-card-subtitle],
+      [matCardTitle], [matCardSubtitle]"></ng-content>
 </div>
 <ng-content select="img"></ng-content>
 <ng-content></ng-content>