types: Add manifest file.

[andrewleech]

Curiously the stdlib/types module missed getting a manifest file in the big migration from setup.py to manifest.py perhaps because it was missing the metadata.txt and only had setup.py

[andrewleech]

On a related note...

/micropython-lib/python-stdlib $ for F in *; do if [ ! -f $F/manifest.py ]; then ls $F/manifest.py;fi;done
ls: cannot access 'README.md/manifest.py': Not a directory
ls: cannot access 'bisect/manifest.py': No such file or directory
ls: cannot access 'json/manifest.py': No such file or directory
ls: cannot access 'keyword/manifest.py': No such file or directory

[dpgeorge]

Thanks!