This is a very simple spinner, showing an operation is in progress (such

as content loading from a server). It uses a typical semi-circle image,

the one we have in Djblets, masked to the current color (which allows

some degree of customization).
By itself, this component does not provide any accessibility

information. Due to the various ways this can be used, that's an

exercise left to the consumer. Guidance is provided in the

documentation.

Unit tests pass.
Played with the spinners in Storybook. These are basic so there isn't

much to test.