ENGCOM-8085: Add font weight heavy variable #29773

 - Merge Pull Request #29773 from mrtuvn/magento2:add-font-heavy-variable-to-lib
 - Merged commits:
   1. 977f6ff

Author: magento-engcom-team

lib/web/css/source/lib/variables/_typography.less

@@ -39,11 +39,15 @@
 @font-size__xs: floor(.75 * @font-size__base); // 11px
 
 //  Weights
+@font-weight__hairline: 100;
+@font-weight__extralight: 200;
 @font-weight__light: 300;
 @font-weight__regular: 400;
 @font-weight__heavier: 500;
 @font-weight__semibold: 600;
 @font-weight__bold: 700;
+@font-weight__extrabold: 800;
+@font-weight__heavy: 900;
 
 //  Styles
 @font-style__base: normal;