- Update MUI v4 to v5

- Remove the SCSS dependency completely and use MUI for theming.
- Update - date-fns, @date-io, notistack. Remove - popper.js, sass-loader.
- Cleanup webpack config.
- Port PSQL tool to use MUI themes instead of SCSS theme.
- Theme change will reflect realtime without refreshing pgAdmin.

web/pgadmin/static/css/style.css

@@ -9,3 +9,8 @@
 @import 'node_modules/@simonwep/pickr/dist/themes/monolith.min.css';
 
 @import 'node_modules/uplot/dist/uPlot.min.css';
+
+@import 'node_modules/rc-dock/dist/rc-dock.css';
+@import 'node_modules/@szhsin/react-menu/dist/index.css';
+
+@import './pgadmin.css';