FI-482: Allow error message formatting

[Jammjammjamm]

This branch allows markdown formatting of error messages, mainly so that we can have multiline error messages. You will probably need to run this in a private window to load the new css.

Submitter:

• This pull request describes why these changes were made
• Internal ticket links to this PR
• Internal ticket is properly labeled (Community/Program)
• Internal ticket has a justification for its Community/Program label
• Code diff has been reviewed for extraneous/missing code
• n/a Tests are included and test edge cases
• Tests/code quality metrics have been run locally and pass

Reviewer 1:

Name:

• Code is maintainable and reusable, reuses existing code and infrastructure
  where appropriate, and accomplishes the task's purpose
• The tests appropriately test the new code, including edge cases
• You have tried to break the code

Reviewer 2:

Name:

• Code is maintainable and reusable, reuses existing code and infrastructure
  where appropriate, and accomplishes the task's purpose
• The tests appropriately test the new code, including edge cases
• You have tried to break the code

[arscan]

Seems good to me, no objections.