Satisfy pyright and add markdown link checker

Ruff now requires check argument

Also make mypy happy

Fix setup of python import

This change means we can't specify unbuffered output to python so we
also change the app code to always flush on output.

Fixes issue #15.

Fix determination of plugin dir

Change from pipxx to pipx

Change from setup.py to pyproject.toml

Check for sleep ability at startup, not each run

New version 1.19

Probably better to run as child plugin not within asyncio.run()

Fix startup using asyncio

Change from threads to asyncio

Each plugin is run as an asyncio task rather than a slightly more
resource heavy system thread.

Also make a couple of minor improvements and add a test directory.