copy: declare dependency on types

[andrewleech]

I noticed during installation and use of micropython-copy that it requires the types module.

This PR simply declares this dependency for automatic installation.

[pfalcon]

Thanks, there're certainly more of these, feel free to fix/report them.

Few comments:

• If you'd look into other modules, you'd see that "depends" line takes "direct" name of a module, e.g. "types". Package namespace prefix, "micropython-", will be generated on creating setup.py from it.
• You're right with putting that line last in metadata.txt, that's the convention, please update your another PR when you get a chance.
• Please use a full sentence as a commit title, e.g. "copy: Declare [...]."

I've fixed these here, but hope you'd take care of them if you choose to contribute more.

Pushed/released. Thanks!