Use custom restyler docker image

[yathomasi]

• Problem with Restyler Job #3056822 restyled-io/restyler#204
• The error is Error: Cannot find module '@dvcorg/gatsby-theme-iterative/tailwind.config'
• According to them, they don't download the package and only include them if it was a standard package or want us to use a custom Restyler Image. source
• Guide: https://github.com/restyled-io/restyled.io/wiki/Using-a-Custom-Restyler-Image

Originally posted by @yathomasi in #4550 (comment)