Update README

Author: juliohm

README.md

@@ -187,11 +187,7 @@ transform `isrevertible`, then it should also implement
 
 Contributions are very welcome. Please [open an issue](https://github.com/JuliaML/TableTransforms.jl/issues) if you have questions.
 
-Below are a few transforms that you can contribute:
-
-- [ ] Standardization of column names
-- [ ] Imputation of missing entries
-- [ ] ...any transform that is useful
+We have open issues with missing transforms that you can contribute.
 
 ## Related packages