doc: Actualize information about generating snowball JS files (#10931)

Author: mitya57

doc/internals/contributing.rst

@@ -326,12 +326,11 @@ Debugging tips
 * Set the debugging options in the `Docutils configuration file
   <https://docutils.sourceforge.io/docs/user/config.html>`_.
 
-* JavaScript stemming algorithms in ``sphinx/search/*.py`` (except ``en.py``)
-  are generated by this `modified snowballcode generator
-  <https://github.com/shibukawa/snowball>`_.  Generated `JSX
-  <https://jsx.github.io/>`_ files are in `this repository
-  <https://github.com/shibukawa/snowball-stemmer.jsx>`_.  You can get the
-  resulting JavaScript files using the following command::
-
-      npm install
-      node_modules/.bin/grunt build # -> dest/*.global.js
+* JavaScript stemming algorithms in ``sphinx/search/non-minified-js/*.js``
+  are generated using `snowball <https://github.com/snowballstem/snowball>`_
+  by cloning the repository, executing ``make dist_libstemmer_js`` and then
+  unpacking the tarball which is generated in ``dist`` directory.
+
+  Minified files in ``sphinx/search/minified-js/*.js`` are generated from
+  non-minified ones using ``uglifyjs`` (installed via npm), with ``-m``
+  option to enable mangling.