Bm gulp experiments

[Bianca-Morris]

Changelog:

• Update webpack config, dependencies, and gulp files to move SCSS -> CSS transpilation process to webpack
• Delete outdated npm scripts that handle scss transpilation
• Use webpack 5 clean prop to clean build directory before each build
  • Needed to move some things around in gitignore for this

Todos:

• Need to check some of the more complex UIs -- things that involve Auth0Lock, for instance (since that code is split out of the main bundle)
• Look more into the chunk hashing, build time stuff (does this serve a meaningful purpose? or is a vestige of some long forgotten time??? can be replaced with native webpack options? not sure)
• Make some attempts at moving the rest of the dev build process out of gulp and to webpack
• Look into what it would take to get hot re-loading working for SCSS, JS? Symlinked repos?