Is your feature request related to a problem? Please describe.
I would like to use features of the TOML 1.0.0 specification, but the current vendored library is only compatible with v0.5.0

Describe the solution you'd likeUpdate the vendored library to one that is compatible with TOML 1.0.0. See e.g. https://github.com/toml-lang/toml/wiki#v100-compliant

Describe alternatives you've considered
Don't use v1.0.0 features, which makes the TOML file less expressive

Additional context
(specifically, mixed-type arrays)