conf: bump searx version to 0.10.0

docs/conf.py

 # built documents.
 #
 # The short X.Y version.
-version = '0.9.0'
+version = '0.10.0'
 # The full version, including alpha/beta/rc tags.
-release = '0.9.0'
+release = '0.10.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.