change ci to pico-sdk develop

increase version for release

Release 0.9.0 (hathach#716)

* update change log for release
* move changelog into docs/
* more changelog
* increase macro version

Merge pull request hathach#634 from hathach/release-0.8.0

Release 0.8.0

release 0.7.0 with changelog and doc update

more changelog

added changelog file