Strict Typescript - Dropzone, VisuallyHidden (#5566)
* checkboxgroup stately: fixing boolean and undefined assignment
* inlineAlert: better typing on variables
* VisuallyHidden: protecting against nulls
* dropzone stories typescript improvements
* improving visuallyalert tests changes and inlinealert is more accurate
* add tsconfig update for the changes
* removing conflicts
* fixing a partial revert
* dropzone lint fixes
