add unicode version.

Author: kargaranamir

README.md

@@ -1,5 +1,6 @@
 # GlotScript
 Detect the script (writing system) of text based on ISO 15924.
+- Unicode version: 15.0.0
 - The codes were sourced from [Wikipedia ISO_15924](https://en.wikipedia.org/wiki/ISO_15924).
 - Unicode ranges were extracted from [Unicode Character Database](https://www.unicode.org/Public/15.0.0/ucd/Scripts.txt).