Support native TOML support following tox-dev/tox#3353

[paddyroddy]

tox now supports full support TOML support. However, for this plugin to work, one still needs to use the legacy_ini_support. Is it possible to adapt this new format?

[ymyzk]

Thanks for opening a discussion. I didn't know that tox now supports TOML natively. It's a good idea to implement it for tox-gh-actions as well. I'll look into more details shortly.