C++20 language standard option

[Holger Strauss]

Please add/change C++20 language standard option -std=c++20. The available -std=c++2a does not seem to have the same effect (checked by manually adding the -std=c++20 option).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[かめのこにょこにょこ]

fixed in v0.6.4. thanks!