In this PR, it is added CircularProgress type and made
AnimatedCircularProgress type extend it.
These types reflect those found in the `src/` directory in `CircularProgress.js` and
`AnimatedCircularProgress.js` files.
The prop `fill` is marked as required in the propTypes for `CircularProgress` but is optional in the Typescript type declaration. This results in Typescript not complaining when leaving the prop empty, while propTypes generates the following warning during runtime: `Failed prop type: The prop 'fill' is marked as required in 'AnimatedCircularProgress', but its value is 'undefined'.`. The fix is to change the Typescript declaration for `fill` from optional to required.
Adds two new props
* padding - adds space around the circle to allow for a cap that bleeds over without clipping
* renderCap - a function that returns the Svg component to draw
