Add text paragraph into greenwich_base theme, update field template to ensure...

This MR does the following:

design system:

• adds new token-settings pattern
  • documentation is included alongside this pattern
  • it is design to be used as a reference so that we don't need to include massive lists of colors all over the place
• adds new colors.get-color-classes-list() function for color tokens
  • gives us a list of all the colours as classes to make generating these color options easier
• adds new headings.apply-headings-selector mixin
  • moved from one of the other mixins into its own thing
  • as we use unique heading selectors (see documentation) we need a consistent and safe way to refer to headings if we need to make changes to them
• adds new headings.get-heading-classes-list function
  • similar to the colors but with headings - since we support responsive and non responsive tokens this either returns the default or the first set of values for mobile just helps with consistency
• Updates rich-text, `heading` and `svg-icon` components to use the new `token-settings` fields
• smaller fixes
  • removed some redundant debug notices
  • small colour naming fixes and bugs (a few gcd colors would never have displayed)

drupal:

• added drupal specific reset code into main-website and main-gcd files to reduce redundant margin and padding in drupal
• moved the paragraphs--text.html.twig from greenwich_community_directory to greenwich_base (see this PR for the second part of that)
• updated the field template so that if a field uses multiple paragraphs (eg the body field on the information page) it doesn't get smart and try to add extra divs in there which would mess with the patterns.

#81