Sp2ts

What's Changed
* added cc dates for 1999 and 2030 by HuxleyDare in https://github.com/SheffieldSolar/sp2ts/pull/4
* Update transition dates and add a module for generating them by JamieTaylor-TUOS in https://github.com/SheffieldSolar/sp2ts/pull/6

New Contributors
* HuxleyDare made their first contribution in https://github.com/SheffieldSolar/sp2ts/pull/4
* JamieTaylor-TUOS made their first contribution in https://github.com/SheffieldSolar/sp2ts/pull/6

**Full Changelog**: https://github.com/SheffieldSolar/sp2ts/compare/0.2.1...1.0.0

**Full Changelog**: https://github.com/SheffieldSolar/sp2ts/compare/0.2.0...0.2.1

- Fixed severe bug in ts2sp (also affecting dt2sp) whereby some values returned around the start and end of days around clock change were incorrect
- Added arg validation for all public methods (slight performance hit, but performance is still good)
- Added type hints to all public methods
- Substantially improved unit tests