Idea: Bär, Implementation: Ulrike Fischer 2020
Get bearwear with the package manager of your tex system.
If you want to install manually instead download bearwear.dtx and bearwear.ins and run TeX/LaTeX on bearwear.ins to unpack the dtx. Put the extracted bearwear.sty in tex/latex/bearwear/ and update the filename database.
The dtx-file contains the documentation, it should at best be compiled with lualatex.
This package offers commands to design shirts for a tikzbear.
It needs a recent version of pgf and the tikzlings-bears package.