chore: add new theme system warning (#1333)

src/framework/theme/styles/_theming.scss

@@ -11,6 +11,7 @@
 
 @import 'core/mixins';
 @import 'core/functions';
+@import 'core/breaking-notice';
 
 $nb-enabled-themes: () !global;
 $nb-enable-css-variables: false !global;
@@ -187,4 +188,6 @@ $nb-themes-export: () !global;
       @content;
     }
   }
+
+  $temp: nb-breaking-notice-show($theme);
 }

src/framework/theme/styles/core/_breaking-notice.scss

@@ -0,0 +1,25 @@
+$nb-breaking-notice-enable: true !global;
+
+@function nb-breaking-notice-show($theme) {
+
+  @debug '$nb-breaking-notice-enable';
+  @debug $nb-breaking-notice-enable;
+  @debug '$nb-breaking-notice-enable';
+
+  @if($nb-breaking-notice-enable) {
+    /* stylelint-disable string-no-newline */
+    @warn '
+           🔥 🔥 🔥 🔥 🔥 🔥  Nebular Attention 🔥 🔥 🔥 🔥 🔥 🔥
+
+           Starting with version 4.0, Nebular will be upgrading its Theme System.
+           If you use CUSTOM Nebular THEMES
+           please LET US KNOW AT http://bit.ly/2THkjSE
+
+           To supress this warning set $nebular-breaking-notice-enable: false; right before nb-install-global() call.
+
+
+           🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥 🔥';
+  }
+  /* stylelint-enable */
+  @return true;
+}