lifecycle badge maturing is being phased out

[bart1]

The guide for authors: https://devguide.ropensci.org/authors-guide.html currently refers to the lifecycle badge maturing. As this is currently not included in lifecycle anymore: https://lifecycle.r-lib.org/articles/stages.html#maturing it might be good to look for an alternative. However there seems to be nothing between experimental and stable so I'm unsure what the fix would be.

[mpadge]

Thanks @bart1. It'd be great if you could PR corresponding changes. I'd say simply replacing "maturing" with "stable" would be best, so

when the package is at least Maturing stable.

Thanks!