Truncate markdown text in editor when switching between markdown and rich text

The following discussion from !104463 (merged) should be addressed:

• @gdoyle started a discussion:

  @himkp I did notice one thing responsively that could be handled in a follow-up. When you switch from markdown to rich text at the smallest screen size, the height jumps around because of the help text being provided to the left of the switcher. We could brainstorm ways how to truncate the text so that doesn't happen in a separate issue.

  cc: @jmiocene