[3.13] gh-123905: Update TOML description to include version number (GH-123906) ...

[3.13] gh-123905: Update TOML description to include version number (GH-123906) (#123908)

gh-123905: Update TOML description to include version number (GH-123906)

Update TOML description to include version number

There is some movement, currently blocked, that would update the TOML spec to 1.1.0; this would include breaking changes to what characters are allowed. Thus, it is worthwhile for the library page to be clear which version is implemented here.

(cherry picked from commit 1b29f4144cb1631650b9b7f467453b5959fa237f)

Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Paul Hoffman <phoffman@proper.com>