Add an example of how to define a custom bot client

[arsena]

When chatpickle pre-designed bot clients do not meet your use case, you can create your own custom bot client.

Provide a new example project with how to do this.

Demonstrates:

• initializing async data
• speaking with the bot
• fetching data elements
• chatpickle configuration
• feature files

[arsena]

Merged into main branch. complete.