[gcc r13-4362] ada: doc/share/conf.py: Switch the HTML documentation to using the RTD theme

[Marc Poulhi?s <dkm@gcc.gnu.org>]

https://gcc.gnu.org/g:81885f5cca22fe82adbe90eb1a5f7808fc083bec

commit r13-4362-g81885f5cca22fe82adbe90eb1a5f7808fc083bec
Author: Joel Brobecker <brobecker@adacore.com>
Date:   Fri Nov 25 17:53:53 2022 +0400

    ada: doc/share/conf.py: Switch the HTML documentation to using the RTD theme
    
    This commit adjust the sphinx configuration to use the "Read The Docs"
    theme, which has the advantage of allowing the navigation bar
    (containing among other things a search bar, and the TOC) to stay
    fixed while scrolling the contents of the page being read. This is
    particularly useful to allow access to those features while reading
    a long page, for instance.
    
    gcc/ada/
    
            * doc/share/conf.py (extensions): Add 'sphinx_rtd_theme'.
            (html_theme): Set to 'sphinx_rtd_theme'.

Diff:
---
 gcc/ada/doc/share/conf.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/doc/share/conf.py b/gcc/ada/doc/share/conf.py
index bb36bfa0c6a..9ab80e7759e 100644
--- a/gcc/ada/doc/share/conf.py
+++ b/gcc/ada/doc/share/conf.py
@@ -92,7 +92,7 @@ if doc_name == 'gnat_rm':
     exclude_patterns.append('share/gnat_project_manager.rst')
     print('ignoring share/gnat_project_manager.rst')
 
-extensions = []
+extensions = ['sphinx_rtd_theme']
 templates_path = ['_templates']
 source_suffix = '.rst'
 master_doc = doc_name
@@ -107,7 +107,7 @@ release = get_gnat_version()
 
 pygments_style = None
 tags.add(get_gnat_build_type())
-html_theme = 'sphinxdoc'
+html_theme = 'sphinx_rtd_theme'
 if os.path.isfile('adacore_transparent.png'):
     html_logo = 'adacore_transparent.png'
 if os.path.isfile('favicon.ico'):