Reformat contributor appreciation on --help screen

[xeruf]

Just adding in some https://sembr.org in a way that also makes it a little more functional:
My terminal (Konsole) tried to open https://github.com/jrnl-org/jrnl. on Ctrl-Click, which obviously fails.
That is now corrected.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[wren]

Thank you!