[semver:minor] Compatibility fixes and LGPL license

As with psyplot 1.4.0, psy-maps is now continuously tested and deployed with CircleCI.

Fixed
-----

-   psy-maps is now officially licensed under LGPL-3.0-only, see [#36](#36)
-   A bug has been resolved that crash makes unstructured plots fill the entire area on zooming in, see [#40](#40)
-   psy-maps is now compatible with cartopy 0.19 and 0.20

Added
-----

-   psy-maps does now have a CITATION.cff file, see <https://citation-file-format.github.io>

Changed
-------

-   Documentation is now hosted with Github Pages at <https://psyplot.github.io/psy-maps>. Redirects from the old documentation at https://psy-maps.readthedocs.io have been configured.
-   Examples have been removed from the psy-maps repository as they now live in a central place at <https://github.com/psyplot/examples>
-   We use CicleCI now for a standardized CI/CD pipeline to build and test the code and docs all at one place, see [#35](#35)

CHANGELOG.rst

@@ -14,6 +14,12 @@ Fixed
   area on zooming in, see `#40 <https://github.com/psyplot/psy-maps/pull/40>`__
 - psy-maps is now compatible with cartopy 0.19 and 0.20
 
+
+Added
+-----
+- psy-maps does now have a CITATION.cff file, see https://citation-file-format.github.io
+
+
 Changed
 -------
 - Documentation is now hosted with Github Pages at https://psyplot.github.io/psy-maps.