Bump sphinx-rtd-theme from 2.0.0 to 3.0.1 (#661)

* Bump sphinx-rtd-theme from 2.0.0 to 3.0.1

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 2.0.0 to 3.0.1.
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](https://github.com/readthedocs/sphinx_rtd_theme/compare/2.0.0...3.0.1)

---
updated-dependencies:
- dependency-name: sphinx-rtd-theme
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* remove call to get_html_theme_path

according to deprection warning of sphinx-rtd-theme>=3

* disable broken spelling integration (pypi) and fix spelling

* fix spelling

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Patrick Kanzler <dev@pkanzler.de>

doc/spelling_wordlist.txt

@@ -87,14 +87,18 @@ config
 del
 dev
 dialout
+docstring
 docstrings
 ean
 Ean
 encodable
 Errno
 fff
+formatter
 fullimage
+hw
 io
+img
 json
 latin
 libusb
@@ -104,16 +108,23 @@ natively
 php
 pre
 prefilled
+preprocess
+preprocessing
 printcap
 programmatically
 py
 pypy
+pyserial
+pyusb
 pyyaml
+pywin
 px
 qrcode
 Raspbian
+readthedocs
 rebase
 rebased
+renderer
 resetted
 rst
 submodule
@@ -122,11 +133,13 @@ src
 testcases
 th
 Todo
+tox
 traceback
 udev
 usb
 USBTimeoutError
 usec
 virtualenvs
+viivakoodi
 whitespaces
 xml