Build: use webpack for production and dev builds

[alexpaxton]

Problem:

• We are using Rollup for production builds and Webpack for development builds (aka storybook)
  • Having two build tools is hard to understand
  • Makes it harder for anyone to work on Clockface if they have to rebuild context every time
• Currently experiencing some disparities between development vs production builds
  • Exporting / referencing image assets is currently not working correctly

Proposed Solution:

• Replace Rollup with Webpack for production builds
  • This should make it simpler to solve the image asset issue
  • Also makes it simpler to implement build changes in the future

[alexpaxton]

Connecting https://github.com/influxdata/clockface/issues/471

[mavarius]

@hoorayimhelping Is this something we still desire to do?