multi: Add proposal details page.

[victorgcramos]

This PR adds the Proposal Details page, including all common-ui
components, and all core methods required for fetching proposal
details.

• core:
  • Add Record Details thunk
  • Add Record details utils
• common-ui:
  • Add LabelValueList component
  • Add RecordToken component
• pi:
  • Proposal Details component
  • Common proposal components
  • /record/:token endpoint to render Proposal Details page

UI changes

TODO:

• Integrate Comments (comments: add Comments Plugin #2724)
• Proposal Diff (feat(common-ui): Add Markdown component. #2741)
• Download Links
• Use default Layout (multi: Add Default Pi Layout on Home Page #2748)
• Use Pi Summaries for proposal status tags

Dependencies

• feat(common-ui): Add Markdown component. #2741
• comments: add Comments Plugin #2724

[victorgcramos]

Preview Update:

[victorgcramos]

Preview:

[tiagoalvesdulce]

LGTM. Great job!

Two small details:

1. The user link isn't working on proposals list and proposal details.
2. When a proposal is already cached and you navigate to it from the proposals list the scroll height from the home page is being persisted to the details page. Ideally it would go back to the top in the details page but keep it for the home page list if the user navigate back.