Epic for CSS System Overhaul

[brdunfield]

Towards #1106

Background information:

Notify's current CSS system is overly complicated and difficult to work with. At times, making CSS changes can be difficult to impossible, due to nested stylesheets imported from multiple repos. This makes it difficult to determine where changes need to be made in order to have an effect.

Earlier in 2020, Tim redid the Notify homepage using tailwind.css, outside of the existing system: https://github.com/cds-snc/notification-homepage

Steps:

I will break these down into other cards and link to them once they exist:

• Further Investigate Tim's solution, and decide whether we want to commit to it for the entirety of Notify or not Make a final decision on whether we want to adopt Tailwind for CSS #1133
• Merge notification-homepage into notification-admin Merge notification-homepage into notification-admin #1134
• Create new component system Design new component system / styles #1135
• update the style guide page https://notification.alpha.canada.ca/_styleguide Implement new component system / styles on the style guide page #1136
• Begin rolling out the new CSS to Notify pages Roll out new CSS system to existing Notify pages #1137
• Once all pages are running on the new system, clean up and remove old CSS Clean up and Remove old CSS #1138