add: alwaysUseEndAngle prop to Circle.js

[cwnicoletti]

I noticed in Circle.js that endAngle is only used when indeterminate is true. I figured there is a reason for this, so I decided to add another prop called alwaysUseEndAngle. Which enables endAngle whether the loader is indeterminate or not.

Also, I'm not sure if you'd like this added to the README or not, I'm assuming you do and I did so in this PR, but you never know! so let me know

[oblador]

Suggested change

	endAngle={(indeterminate ? endAngle * 2 : alwaysUseEndAngle ? endAngle * 2 : 2) * Math.PI}
	endAngle={(indeterminate || alwaysUseEndAngle ? endAngle * 2 : 2) * Math.PI}

[oblador]

Thanks for your PR! Might I ask what your use case is for this? Also would you mind adding type definitions for this new prop too? Thx!