fix(demo): fix theme issue

Author: joejordanbrown

src/app/core/themes/deeppurple-amber.scss

@@ -1,5 +1,4 @@
-@import '~@angular/material/theming';
-
+@import '~@angular/material/_theming';
 
 // Include non-theme styles for core.
 @include mat-core();

src/app/core/themes/indigo-grey.scss

@@ -1,4 +1,4 @@
-@import '~@angular/material/theming';
+@import '~@angular/material/_theming';
 
 // Include non-theme styles for core.
 @include mat-core();

src/app/core/themes/indigo-pink.scss

@@ -1,4 +1,4 @@
-@import '~@angular/material/theming';
+@import '~@angular/material/_theming';
 
 // Include non-theme styles for core.
 @include mat-core();

src/app/core/themes/pink-bluegrey.scss

@@ -1,7 +1,5 @@
 @import '~@angular/material/_theming';
 
-
-
 // Include non-theme styles for core.
 @include mat-core();
 

src/app/core/themes/pink-grey.scss

@@ -1,7 +1,5 @@
 @import '~@angular/material/_theming';
 
-
-
 // Include non-theme styles for core.
 @include mat-core();
 

src/app/core/themes/purple-green.scss

@@ -1,6 +1,4 @@
-@import '~@angular/material/theming';
-
-
+@import '~@angular/material/_theming';
 
 // Include non-theme styles for core.
 @include mat-core();

src/styles.scss

@@ -6,6 +6,7 @@
 @import './app/core/themes/pink-bluegrey';
 @import './app/core/themes/pink-grey';
 @import './app/core/themes/indigo-pink';
+@import './app/core/themes/indigo-grey';
 @import './app/core/themes/purple-green';