[IMP] developer: improve navigation in top-level pages

Prior to this commit, users had to either know in advance or guess the
location of the content they were looking for. Top-level pages of the
"Developer" section of the documentation, in particular the "Developer"
page itself, were listing their sub-pages without directions for users.

This commit brings the following changes to improve the navigation:
- add directions for users on the "Developer" page and list the three
  main categories of developer documentation ("Tutorials", "How-to
  guides", and "Reference") with explanations of their content and
  target audience;
- add categories for content cards on the "Tutorials" and "How-to
  guides" pages, and fine-tune the toctree of the "Reference" page to
  more easily locate specific topics;
- clarify what are the "Python framework" and the "JavaScript framework"
  by relabelling them to "Server framework" and "Web framework" on
  top-level pages, as some users were confused to find that the JS
  framework was not responsible for the server, and others that the
  documentation for QWeb template is located in the Python documentation;
- extract the "Setup guide" from the "Getting started" tutorial and
  rename the latter to "Server framework 101" to allow reusing the setup
  guide in other tutorials and make clear that the "Server framework 101"
  tutorial is not about the Web framework.

task-3802536

closes odoo/documentation#8712

X-original-commit: 7f623b6ad5
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>
Co-authored-by: Valeriya (vchu) <vchu@odoo.com>

content/developer/tutorials/discover_js_framework.rst

@@ -1,8 +1,8 @@
 :show-content:
 
-=========================
-Discover the JS framework
-=========================
+==========================
+Discover the web framework
+==========================
 
 .. toctree::
     :titlesonly:
@@ -10,12 +10,12 @@ Discover the JS framework
 
     discover_js_framework/*
 
-This two parts tutorial is designed to introduce you to the basics of the Odoo Javascript framework. Whether
+This two parts tutorial is designed to introduce you to the basics of the web framework. Whether
 you are new to the framework or have some prior experience, this tutorial will provide you with a
-solid foundation for using the Odoo JavaScript framework in your projects.
+solid foundation for using the web framework in your projects.
 
 The first part covers the basics of Owl components, which
-are a key part of the Odoo JS framework. Owl components are reusable UI components that can be used
+are a key part of the web framework. Owl components are reusable UI components that can be used
 to build complex web interfaces quickly and efficiently. We will explore how to create and use Owl
 components in Odoo. Then, in the second part of this tutorial, we focus on creating a dashboard using various
 features of Odoo. Dashboards are an essential part of any web application, and provide a nice starting
@@ -23,8 +23,7 @@ point to use and interact with the Odoo codebase.
 
 This tutorial assumes that you have some basic knowledge of development with Odoo in general
 (models, controllers, QWeb, ...). If you are new to Odoo, we recommend that you start with the
-:doc:`Getting started </developer/tutorials/getting_started>` tutorial before proceeding with this
-one.
+:doc:`/developer/tutorials/server_framework_101` tutorial before proceeding with this one.
 
 .. note::