Typo fix

Changed "mean" to "meant"

Author: disisisid

src/lib/README.md

@@ -4,5 +4,5 @@ The files within this directory are used to generate `lib.d.ts` and `lib.es6.d.t
 
 ## Generated files
 
-Any files ending in `.generated.d.ts` aren't mean to be edited by hand.
+Any files ending in `.generated.d.ts` aren't meant to be edited by hand.
 If you need to make changes to such files, make a change to the input files for [**our library generator**](https://github.com/Microsoft/TSJS-lib-generator).