Add type definitions

[thegecko]

Resolves #65

Tested in a TypeScript project using both callback and promise forms of find as well as plug/unplug events.

Events aren't typed, so accept any event name, but should suffice in most cases.

[MadLittleMods]

Is the types/ directory standard practice vs just putting it alongside the file? (examples?)

[thegecko]

There isn't really a convention, I personally prefer to keep the types separate.
The TypeScript docs has you put the types next to the JS files. I've updated the PR to do that instead.

[MadLittleMods]

Thanks for the contribution @thegecko

This is now part of 3.2.0. I'm waiting to publish to npm until the prebuild binaries are available, https://github.com/MadLittleMods/node-usb-detection/releases/tag/v3.2.0