package.json: Use real names and add current maintainers

This makes our npm page look more maintained.

Using real names are specified by https://www.npmjs.org/doc/files/package.json.html#people-fields-author-contributors

Some maintainers are not added because:

- the person is the author, or
- the person chose to be private in the jadejs organization.

Conversely, some private maintainers are in the package.json because they are
already in it when I got it.

Signed-off-by: Timothy Gu <timothygu99@gmail.com>