perf(css): improve browser performance by adding css contain property

Author: jyounce

src/client/styles/main/host.scss

@@ -0,0 +1,6 @@
+/*******
+ * HOST
+ *******/
+:host {
+	contain: content;
+}

src/client/styles/rb-checkbox.scss

@@ -4,6 +4,7 @@
 @import 'sass/functions.scss';
 @import 'sass/colors/palette.scss';
 @import 'sass/colors/form-control.scss';
+@import 'main/host.scss';
 
 /* The Component
  ****************/