Enable full no-std use

Make sure the Changelog is available

Bump version number to v0.7.0

Softlink license & readme

Update to 2024b

Update to tzdb 2024 (#202)

* Update to tzdb 2024

Upstream changelog: <https://mm.icann.org/pipermail/tz-announce/2024-February/000081.html>

* Update badges

Ensure that all time zones are contained (#200)

Doubly nested time zone like "America/Argentina/Buenos_Aires" were
missing.

Update changelog

Add `tzdb_data` crate (#197)

Splitting up the generated data makes maintenance easier.

Fix no-std