Display markdown in activities

[joanagmaia]

Changes proposed ✍️

• Added marked package to handle markdown parsing
• Added html.scss file to allow for proper list styling in parsed html
• Update sanitization rules to allow for markdown checklists (checkboxes)
• Create a marked plugin to reuse the parse function globally throughout the components

Relates to task
Relates to issue

Screenshots (front-end changes only)

Checklist ✅

• Label appropriately with Feature, Enhancement, or Bug.
• Tests are passing.
• New backend functionality has been unit-tested.
• Environment variables have been updated:
  • Local frontend configuration: frontend/.env.dist.local, frontend/.env.dist.composed.
  • Local backend: backend/.env.dist.local, backend/.env.dist.composed.
  • Configuration docs have been updated.
  • Team members only: update environment variables in override, staging and production env. files and trigger update config script.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.
• All changes have been tested in a staging site.
• All changes are working locally running crowd.dev's Docker local environment.

[mariobalca]

Looks good to me!
The only thing that we need to keep in mind, but it's not a blocker to merge, is that by using a plugin, $marked won't be available to use within components built with the Composition API — we might need to create a component (with the Options API) just to render markdown with this new plugin (as well as the sanatize one).
Other that that, great job! Thanks for taking care of this 🙌