Update typescript types

[mark-buer]

Fixes for the d.ts file, which seems to have stagnated.

At present, the type info included with v2.0.0-beta.2 is wrong/incomplete in a few places.

Thus, could a beta release please be made with this change?

I license my contributions to the DerivableJS project under the Apache License 2.0.

[ds300]

Nice, thanks!

hmm working on a publish, hold on

[ds300]

@mark-buer published under derivable@2.0.0-beta.3 – thanks again!

[mark-buer]

Speedy! 👍