fix the lack of lack

Author: telephon

README.md

@@ -4,7 +4,7 @@
 
 The JSON implementation of the SuperCollider standard library lacks certain features such as
 
-* [ ] lack of a JSON encoder (the conversion of an dictionary to a JSON string)
+* [ ] a JSON encoder (the conversion of an dictionary to a JSON string)
 * [ ] parsing JSON values into their respective type (`.parseJSON` converts everything to a string)
 
 which this Quark implements, building on top of the existing implementation.