docs: mark external

Signed-off-by: Jan Kowalleck <jan.kowalleck@gmail.com>

Author: jkowalleck

docs/conf.py

@@ -68,6 +68,10 @@
 #
 html_theme = 'sphinx_rtd_theme'
 
+html_theme_options = {
+    'style_external_links': True,
+}
+
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".