Release v0.2

# grtsdb 0.2

* Add a vignette on the basic usage.
* Added a `NEWS.md` file to track changes to the package.
* New features `add_legacy_site()`, `drop_legacy_sites()` and
  `extract_legacy_sample()`.
  These functions improve the ranking of legacy sites.
* Bugfix when restoring a compacted database (#2).

Version 0.1

Version used to draw to sample in 10.5281/zenodo.2784012