[Docs] Clarify the rules.mk setup for Unicode (#6286)

* Clarify the rules.mk setup for Unicode

* code point

Co-Authored-By: Konstantin Đorđević <vomindoraan@gmail.com>

* Remove "your"

Co-Authored-By: Konstantin Đorđević <vomindoraan@gmail.com>

* Undo a line change

Co-Authored-By: Konstantin Đorđević <vomindoraan@gmail.com>

* dot the comma

Co-Authored-By: Konstantin Đorđević <vomindoraan@gmail.com>

* Update docs/feature_unicode.md

Co-Authored-By: Konstantin Đorđević <vomindoraan@gmail.com>