update readme for UFCS description

Co-authored-by: Jan Jurzitza <[email protected]>

Author: vushu

README.md

@@ -38,6 +38,7 @@ the issue.)
 	* Simple UFCS suggestions for concrete types.
 * Not working:
 	* UFCS completion for templates, literals, UFCS function arguments, and '.' chaining with other UFCS functions.
+	* UFCS calltips
 	* Autocompletion of declarations with template arguments (This will work to some extent, but it won't do things like replace T with int)
 	* Determining the type of an enum member when no base type is specified, but the first member has an initializer
 	* auto functions (which can then propagate the failure to auto declarations)