Add Lines of Code badge to README

Author: kojix2

README.md

@@ -1,6 +1,7 @@
 # YouPlot2
 
 [![build](https://github.com/red-data-tools/YouPlot2/actions/workflows/build.yml/badge.svg)](https://github.com/red-data-tools/YouPlot2/actions/workflows/build.yml)
+[![Lines of Code](https://img.shields.io/endpoint?url=https%3A%2F%2Ftokei.kojix2.net%2Fbadge%2Fgithub%2Fred-data-tools%2FYouPlot2%2Flines)](https://tokei.kojix2.net/github/red-data-tools/YouPlot2)
 
 [YouPlot2](https://github.com/red-data-tools/YouPlot2) is an experimental [Crystal](https://github.com/crystal-lang/crystal) rewrite of [YouPlot](https://github.com/red-data-tools/YouPlot).