[FEATURE] Support GBFS

[yu-ta-sato]

Contributing guidelines

• I understand the contributing guidelines

Documentation

• My proposal is not addressed by the documentation or examples

Existing issues

• Nothing similar appears in an existing issue

Is your feature request related to a problem? Please describe.

Like GTFS, GBFS for bike services could be supported.

Describe the solution you'd like

• Addload_gbfs()
• Enhance travel_summary_graph()

Describe alternatives you've considered

No response

API changes

Additional context

No response