fix incorrect default export type as mentioned in issue #33

[atombrenner]

As mentioned in Issue #33 , the typing in index.d.ts incorrectly declared a default export, but index.js has no default export. This caused issues with Node16/CommonJS module settings and having esModuleInterop set to false. (More details.)
This fix deliberately changes only the type definition (to be exact, the generator for the type definition).
Because the package also exports types, the fix suggested in #33 was not enough. To be able to export types with the old syntax, I had to add a namespace declaration in which the exported types are nested.

As a drive-by change, the tsd dependency (tool for testing type definitions) was also updated to the newest version.

This change might break clients that applied one of the suggested workarounds in issue #33 as the types are now correct.
Clients not affected should see no changes.

[lovell]

LGTM, thank you for the PR. As you say, this looks like a breaking change, but the workaround appears to include the use of as unknown so I think we're OK for a patch version. Will wait for feedback from others before merging.

[atombrenner]

@lovell are we good to merge and release now?

[lovell]

2.0.2 now available with this fix, thank you.