Docs: Add robots.txt to only allow indexing of latest and stable (

#6517)

Currently, all versions of the documentation are indexed with the result
that google searches come up with very outdated versions and the latest
version is almost impossible to find. The `robots.txt` now disallows
any path from being indexed except for the `latest` and `stable`
versions of the documentation.

docs/source/conf.py

@@ -171,6 +171,9 @@
 # If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
 html_show_copyright = False
 
+# This is to tell search engines to index only stable and latest version
+html_extra_path = ['robots.txt']
+
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 

docs/source/robots.txt

@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /projects/aiida-core/en/latest/
+Allow: /projects/aiida-core/en/stable/
+Disallow: /