fix typo

Author: paulclark

Readme.md

@@ -77,7 +77,7 @@ properties for consistency.
 
 ## AST
 
-Interatively explore the AST with <http://iamdustan.com/reworkcss_ast_explorer/>.
+Interactively explore the AST with <http://iamdustan.com/reworkcss_ast_explorer/>.
 
 ### Common properties