Bump added-value from 0.14.2 to 0.15.0 in /docs (#1855)

Bumps [added-value](https://github.com/sixty-north/added-value) from 0.14.2 to 0.15.0.
- [Release notes](https://github.com/sixty-north/added-value/releases)
- [Changelog](https://github.com/sixty-north/added-value/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/sixty-north/added-value/commits)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -6,7 +6,7 @@ sphinx_autodoc_typehints==1.11.1
 sphinxcontrib-mermaid==0.6.0
 recommonmark==0.7.1
 m2r2==0.2.7
-added-value==0.14.2
+added-value==0.15.0
 tomlkit==0.7.0
 docutils==0.16