README.md: Mention tmux input-buffer-size option for tmux version >= 3.6#23

ktetzlaff wants to merge 1 commit into

wookayin:masterwookayin/python-imgcat:masterfrom

ktetzlaff:tmux-36-input-buffer-sizektetzlaff/python-imgcat-fork:tmux-36-input-buffer-sizeCopy head branch name to clipboard