Bump sphinx-rtd-theme from 0.5.0 to 0.5.1 (#42)

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 0.5.0 to 0.5.1.
- [Release notes](https://github.com/readthedocs/sphinx_rtd_theme/releases)
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@0.5.0...0.5.1)

Signed-off-by: dependabot[bot] <[email protected]>

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

Author: dependabot[bot]

setup.py

@@ -10,7 +10,7 @@
     license='MIT',
 
     packages=['sponge_docs_theme'],
-    install_requires=['sphinx_rtd_theme==0.5.0'],
+    install_requires=['sphinx_rtd_theme==0.5.1'],
 
     message_extractors={
         'src/theme/js': [