The TypeScript definition erroneously made `options` required. We can
fix it by providing a default value, which means users calling the
function will be able to leave it blank without TS complaining.
Issues like this are a +1 to porting our tests to TypeScript in order to
catch these on our own test suite, so that's something we should look into.
This adds the new docs that are generated by API Extractor via TSDoc.
They are sparse because we do not yet use TSDoc in the codebase. This is
the starting point and from here we can work through all the different
classes and improve the documentation.