feature request: support poetry dependency groups

[purificant]

Poetry can organise dependencies into "groups": https://python-poetry.org/docs/managing-dependencies/#dependency-groups

Two common groups are used by default:
"main", an implicit group under key "[tool.poetry.dependencies]"
"dev", under key "[tool.poetry.group.dev.dependencies]"

At the moment, the pip-check-updates parser will ignore other groups, for example "[tool.poetry.group.foo.dependencies]", where group name is "foo".

This feature request is to parse and detect updates for poetry groups other than "dev" and "main".

Links to relevant source code: https://github.com/zehengl/pip-check-updates/blob/main/src/pip_check_updates/parser.py#L152
See method "_load_poetry"