v3.2 for MuseScore 3
Plugin tested on MuseScore 3 v3.2.3. Note that this is not compatible with MuseScore versions 3.4 and above (January 2020) when the offset was changed, so that the tabs no longer line up correctly.
The font file is attached for convenience from Blayne Chastain and states:
Tin Whistle Tab font is free of charge for both personal and commercial use. Distribution for a fee is not allowed. Please credit Blayne Chastain in any publication in which this font appears with the following copyright notice: "Tin Whistle Tab font © Blayne Chastain / www.blaynechastain.com"