update stories to use storybook 6 main.js

Author: stomita

.storybook/addons.js

@@ -0,0 +1,11 @@
+const path = require('path');
+
+module.exports = {
+  stories: ['../stories/**/*Stories.tsx'],
+  addons: [
+    '@storybook/addon-docs',
+    '@storybook/addon-actions',
+    '@storybook/addon-knobs',
+    'storycap',
+  ],
+};

.storybook/config.js

@@ -1,9 +1,7 @@
 <script>
 (function() {
   var stylesheetUrl =
-    (/\.sbook\.io$/.test(location.hostname) ? "//mashmatrix.github.io/react-lightning-design-system" :
-     location.hostname === "mashmatrix.github.io" ? "/react-lightning-design-system" :
-     "") +
+     (location.hostname === "mashmatrix.github.io" ? "/react-lightning-design-system" : "") +
     "/assets/styles/salesforce-lightning-design-system.min.css";
   var link = document.createElement('link');
   link.href = stylesheetUrl;