inputButtonConfig was removed, but not update in docs

[amir14a]

Hi, I use latest version of your package(7.0.4), in this version, there is no inputButtonConfig property and InputButtonConfig class, but you don't include this in your documents, there is no migration guide for this, and you use this property in the last example in your docs, please update your docs

[clragon]

sorry about that! 7.0.1 was actually a breaking change and I replaced InputButtonConfig with KeyPadConfig. I have added this to the migration guide in the readme. #89 should fix the docs accordingly!