[doc] Fix broken links following toc reorganization

Author: Pierre-Sassoulas

README.rst

@@ -95,7 +95,7 @@ For command line use, pylint is installed with::
 It can also be integrated in most editors or IDEs. More information can be found
 `in the documentation`_.
 
-.. _in the documentation: https://pylint.pycqa.org/en/latest/user_guide/installation.html
+.. _in the documentation: https://pylint.pycqa.org/en/latest/user_guide/installation/index.html
 
 Contributing
 ------------
@@ -122,7 +122,7 @@ You can place this badge in your README to let others know your project uses pyl
 
 Learn how to add a badge to your documentation in the `the badge documentation`_.
 
-.. _the badge documentation: https://pylint.pycqa.org/en/latest/user_guide/badge.html
+.. _the badge documentation: https://pylint.pycqa.org/en/latest/user_guide/installation/badge.html
 
 License
 -------

doc/conf.py

@@ -75,6 +75,7 @@
     "messages/messages_list": "../user_guide/messages/messages_overview.html",
     "support": "contact.html",
     "technical_reference/c_extensions": "../user_guide/messages/error/no-member.html",
+    "technical_reference/extensions": "../user_guide/checkers/extensions.html",
     "technical_reference/checkers": "../development_guide/technical_reference/checkers.html",
     "technical_reference/features": "../user_guide/checkers/features.html",
     "technical_reference/index": "../development_guide/technical_reference/index.html",

doc/whatsnew/2.9.rst

@@ -19,7 +19,7 @@ new checks optional is a step in that direction. In order to do that we
 created an optional code style checker that can be loaded using
 ``pylint.extensions.code_style`` with the ``load-plugins`` options.
 More than ever, if as a veteran you want the most checks you can possibly get,
-`you should check the list of pylint extensions. <https://pylint.pycqa.org/en/latest/technical_reference/extensions.html#optional-pylint-checkers-in-the-extensions-module>`_.
+`you should check the list of pylint extensions. <https://pylint.pycqa.org/en/latest/user_guide/checkers/extensions.html#optional-pylint-checkers-in-the-extensions-module>`_.
 
 
 New checkers