Update the Unicode vector font unicode.lff

Take the latest changes from:
https://github.com/LibreCAD/LibreCAD/commits/master/librecad/support/fonts/unicode.lff

£ - Crash fixed
	"fixed various issues in LFF font files"
є
	"Correct "[0454] є" character in unicode.lff"
Greek alphabet added
	"added greek characters to unicode.lff [ci skip]"
⁵
	"add superscript 5 to all fonts"

Chinese characters added and updated from "new unicode.lff.gz" posted
by @liuxilu here:
solvespace#1042 (comment)