Fix docs typo (#10)

Author: dezren39

index.d.ts

@@ -1,7 +1,7 @@
 /**
 Get the real length of a string - by correctly counting astral symbols and ignoring [ansi escape codes](https://github.com/sindresorhus/strip-ansi).
 
-`String#length` errornously counts [astral symbols](https://web.archive.org/web/20150721114550/http://www.tlg.uci.edu/~opoudjis/unicode/unicode_astral.html) as two characters.
+`String#length` erroneously counts [astral symbols](https://web.archive.org/web/20150721114550/http://www.tlg.uci.edu/~opoudjis/unicode/unicode_astral.html) as two characters.
 
 @example
 ```

readme.md

@@ -2,7 +2,7 @@
 
 > Get the real length of a string - by correctly counting astral symbols and ignoring [ansi escape codes](https://github.com/sindresorhus/strip-ansi)
 
-`String#length` errornously counts [astral symbols](https://web.archive.org/web/20150721114550/http://www.tlg.uci.edu/~opoudjis/unicode/unicode_astral.html) as two characters.
+`String#length` erroneously counts [astral symbols](https://web.archive.org/web/20150721114550/http://www.tlg.uci.edu/~opoudjis/unicode/unicode_astral.html) as two characters.
 
 ## Install