[JS] Update yarn packages and deprecated SCSS syntax

app/javascript/src/styles/base/_vars.scss

@@ -2,8 +2,8 @@
 $border-radius-half: 3px;
 $border-radius-full: 6px;
 $base-padding: 1rem;
-$padding-050: $base-padding/2;
-$padding-025: $base-padding/4;
+$padding-050: $base-padding*0.5;
+$padding-025: $base-padding*0.25;
 $padding-100: $base-padding;
 $padding-125: $base-padding*1.25;
 $padding-150: $base-padding*1.5;

app/javascript/src/styles/common/tables.scss

@@ -56,7 +56,7 @@ table.table {
 
 // Needed so that unconverted tables work.
 table.striped {
-  @extend table.table;
+  @extend .table;
 }
 
 /*
@@ -96,7 +96,7 @@ table.search {
 }
 
 table.aligned-vertical {
-  @extend table.search;
+  @extend .search;
 
   tr {
     height: 1.75em;

babel.config.js

@@ -47,6 +47,7 @@ module.exports = function(api) {
           loose: true
         }
       ],
+      ["@babel/plugin-proposal-private-methods", { "loose": true }],
       [
         require('@babel/plugin-proposal-object-rest-spread').default,
         {