REL: 0.5.5

[carterbox]

Adds a new RegularPolygon class and cleans up the docs a bit.

[pep8speaks]

Hello @carterbox! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file docs/source/conf.py:

Line 156:80: E501 line too long (229 > 79 characters)

• In the file src/xdesign/geometry/area.py:

Line 552:36: W605 invalid escape sequence '\p' Line 553:13: W605 invalid escape sequence '\p'