Fix type declarations for 'shape' and 'mode' for typescript

[drannex42]

The type declaration file had issues when handling, well, types on the options 'shape' and 'mode'. Before the element would not be able to render without either ignoring (so they are set to their default) or directly modifying the type declaration file in your modules directory. This moves them to using 'string' as the type instead of unknown types (such as 'circle' or 'static' for example).

This small fix should make it easier for the typescript users out there.