Transition from sphinx to mkdocs for documentation (#271)

* Transition from sphinx to mkdocs for documentation

* Tidy up docstrings, mkdocs config

* Add logo to docs, hide navbar

* Reformat docstring indentation

* Missing newline

* Fix more wrong indents

* Add `mike` for versioning the docs

* add site dir to gitignore

* setup.py: Remove .so files on cleanup

* header.pxi: Rename all "cpdef enum" to "cdef enum"

cpdef didn't work correctly with Cython 3.0 onwards, which is needed for
the docs. Setting this to "cdef enum" doesn't change any functionality
in our case.

* Remove embedsignature=True

For building docs, we use Cython 3.0 now, which automatically provides
full introspection functionality for cython functions

* Build docs with Cython 3.0

---------

Co-authored-by: Michael Milton <michael.r.milton@gmail.com>
Co-authored-by: Michael Milton <ttmigueltt@gmail.com>

Author: tazend

.gitignore

@@ -1,5 +1,6 @@
 # Ignore Build Directory #
 build/
+site
 
 # Ignore Docs Directory #
 #doc/