test cylc in pyproject toml

pyproject.toml

[build-system]
requires = ["poetry-core>=1.1.0a7"]
# requires pre-release poetry, bedause metomi-isodatetime uses epoch versioning
build-backend = "poetry.core.masonry.api"

[tool.poetry]
name = "my-test"
description = "testing cylc"
version = "0.0.1"
authors = ["Ashley Sommer <[email protected]"]

[tool.poetry.dependencies]
python = "^3.8"
cylc-flow = {version = "8.0rc2", allow-prereleases = true}
metomi-isodatetime = {version = "1!2.0.2", allow-prereleases = true}