[doc] fix warnings/errors in doc build
- fix links to images
- fix a couple of typos
- re-add IDownloadableOneLineView doc
- rename documenting.rst back to .txt, it's intended as a doc of how to
write rst, not part of the rst doc
Related to #4832808
.. _resources:
Locate resources
----------------
.. automethod:: cubicweb.web.webconfig.WebConfiguration.locate_resource
.. automethod:: cubicweb.web.webconfig.WebConfiguration.locate_doc_file
.. automethod:: cubicweb.web.webconfig.WebConfiguration.locate_all_files
Static files handling
---------------------
.. autoattribute:: cubicweb.web.webconfig.WebConfiguration.static_directory
.. automethod:: cubicweb.web.webconfig.WebConfiguration.static_file_exists
.. automethod:: cubicweb.web.webconfig.WebConfiguration.static_file_open
.. automethod:: cubicweb.web.webconfig.WebConfiguration.static_file_add
.. automethod:: cubicweb.web.webconfig.WebConfiguration.static_file_del