Schemdule

Finish one-day schedule in command-line.

Schema

- Add `prompters()` function.
- Use payload generator in cycle function

Prompter

- Add exception free prompt method.

Configuration

- Add global configuration.

Extension

- Add configurable time bound for audioplay and simplegui.

- Add `payloads()` function in schema environment.
- Adjust message generator.
- Support `AudioPayload` in audioplay extension.
- Fix duplicate `UserPayload` wrapper.
- Rename `PrompterPayload` to `Payload`.

- Remove Python 3.6 support.
- Add audioplay extension.
- Redesign payload & prompter interfaces.
- Add emoji 😀 in terminal.

- Add [miaotixing](https://miaotixing.com/) extension
- Test for extension framework

- Add logging
- Add extension detector and list command