Merge branch 'fix-missing-searchbar' into 'preview'

Search bar is gone with material >= 9.0

See merge request !800

Dockerfile

@@ -6,7 +6,7 @@ SHELL ["/bin/bash", "-c"]
 # Base #
 ########
 
-RUN pip install mkdocs>=1.1.2 mkdocs-material>=7.1.0 mkdocs-htmlproofer-plugin==0.8.0 mkdocs-video==1.3.0
+RUN pip install mkdocs>=1.1.2 mkdocs-material==8.5.11 mkdocs-htmlproofer-plugin==0.8.0 mkdocs-video==1.3.0
 
 ##########
 # Linter #