Suggestion: support configuration with pyproject.toml

[sciyoshi]

@Kyle-Verhoog it's almost 2021 - I shouldn't have to add yet another file to the root of my repo ;) would be great if this could read configuration from pyproject.toml if it exists rather than having to add a new riotfile.py.

[Kyle-Verhoog]

hey @sciyoshi 😄!! Yes I think this makes sense.

We had discussed it early on in #15 and opted to proceed with just one avenue of configuration until we got a bit more stable. We're quickly approaching that point, so thanks for bringing it back up for discussion as it's something we did want to do.