Added :class:~.Polygram, rework the polygon inheritance tree, and a…

…dd :class:`~.Star` (#1490)

* Add Polygram, reorder Polygon inheritance around it, add Star

* Add tests

* Spiff up tests and docs

* Avoid spaces allowing a newline in the middle of example coordinate

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix doctest

* Change Polygram.round_corners example

* Change StarExample to show how stars overlap with their regular polygram equivalent

* Apply suggestions from code review

Co-authored-by: Anton Ballmaier <[email protected]>

* Apply docs suggestions

* Change round_corners example to use a star

* Allow any iterable to be passed to Polygram

* Fix tests by converting all vertices to numpy arrays

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Anton Ballmaier <[email protected]>