Bump sphinx-rtd-theme from 1.3.0 to 2.0.0 (#70)

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 1.3.0 to 2.0.0.
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@1.3.0...2.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

sphinx_docs_build/requirements.txt

@@ -1,2 +1,2 @@
-sphinx-rtd-theme==1.3.0
+sphinx-rtd-theme==2.0.0
 purpleair-data-logger==1.3.0a1