fix(mdc-indigo-pink): add mat-core and mat-core-theme to indigo-pink

* Some of the base css was missing without these mixins
  which was causing the button ripple to not work properly.

Author: wagnermaciel

src/material-experimental/mdc-theming/_all-theme.scss

@@ -12,6 +12,7 @@
 @import '../mdc-progress-bar/progress-bar-theme';
 @import '../mdc-input/input-theme';
 @import '../mdc-form-field/form-field-theme';
+@import '../../material/core/core';
 @import '../../material/core/theming/check-duplicate-styles';
 
 @mixin angular-material-mdc-theme($theme-or-color-config) {

src/material-experimental/mdc-theming/prebuilt/indigo-pink.scss

@@ -1,6 +1,9 @@
 @import '../all-theme';
 @import '../../mdc-typography/all-typography';
 
+// Include non-theme styles for core.
+@include mat-core();
+
 // Define a theme.
 $primary: mat-palette($mat-indigo);
 $accent:  mat-palette($mat-pink, A200, A100, A400);
@@ -10,3 +13,4 @@ $theme: mat-light-theme($primary, $accent);
 // Include all theme styles for the components.
 @include angular-material-mdc-theme($theme);
 @include angular-material-mdc-typography();
+@include mat-core-theme($theme);