1.0.0-beta1

Update tests to TOML v1.0.0, and a number of improvements to the test runner tool.

May not be compressive yet; but GitHub needs a release to upload binaries 🤷 Since this requires Go 1.16, that makes it easier to run it from CIs and such.

Some minor incompatibilities in the test tool:

• You no longer need to add a type hint to arrays.
• tests are always referenced as valid/[...] or invalid/[..]
• The datetime-local, date-local, and time-local types are added. You will need to add support for this in your -encode and -decode test helpers.