Add pagination support for (metadata) get base list endpoint

[marks]

Airtable API docs at https://airtable.com/developers/web/api/list-bases note that 1,000 bases are returned per request. You can paginate with an offset param

https://github.com/gtalarico/pyairtable/blob/0f9fd8e7c320b065761033a32d7f0eba0abda3ed/pyairtable/metadata.py#L6-L32 in this library should get updated accordingly