Write a page dedicated to the project manager's UI

Extracted and edited the project manager from
intro_to_the_editor_interface.rst, added it in the tutorials/editor
section
Wrote a short introduction for the editor section

tutorials/editor/index.rst

@@ -2,14 +2,33 @@ Editor manual
 =============
 
 In this section, we cover the Godot editor in general, from its interface to
-using it with the command line. We cover some specific editors' interface in
-other sections where appropriate. For example, the :ref:`animation editor
+using it with the command line.
+
+The editor's interface
+----------------------
+
+The following pages explain how to use the various windows, workspaces, and
+docks that make up the Godot editor. We cover some specific editors' interface
+in other sections where appropriate. For example, the :ref:`animation editor
 <doc_introduction_animation>`.
 
+.. toctree::
+   :maxdepth: 1
+   :name: toc-editor-interface
+
+   project_manager
+   default_key_mapping
+
+For developers
+--------------
+
+The articles below focus on features for developers, like calling Godot from the
+command lines and using an external text editor such as Visual Studio Code or
+Emacs.
+
 .. toctree::
    :maxdepth: 1
    :name: toc-learn-editor
 
    command_line_tutorial
    external_editor
-   default_key_mapping

tutorials/editor/project_manager.rst

@@ -0,0 +1,75 @@
+.. _doc_project_manager:
+
+Using the Project manager
+=========================
+
+When you launch Godot, the first window you see is the Project Manager. It lets
+you create, remove, import, or play game projects.
+
+.. image:: img/editor_ui_intro_project_manager_01.png
+
+In the window's top-right corner, a drop-down menu allows you to change the
+editor's language.
+
+.. image:: img/editor_ui_intro_project_manager_02.png
+
+Creating and importing projects
+-------------------------------
+
+To create a new project:
+
+1. Click the ``New Project`` button on the right of the window.
+2. Give the project a name, choose an empty folder on your computer to save the
+   files, and select a rendering backend.
+3. Click the Create & Edit button.
+
+.. image:: img/editor_ui_intro_project_manager_04.png
+
+.. seealso:: For more information about rendering backends, see
+             :ref:`doc_gles2_gles3_differences`.
+
+Using the file browser
+~~~~~~~~~~~~~~~~~~~~~~
+
+Click the Browse button to open Godot's file browser and pick a location or type
+the folder's path in the Project Path field.
+
+.. image:: img/editor_ui_intro_project_manager_05.png
+
+When you see the green tick on the right, it means the engine detects an empty
+folder. You can also click the ``Create Folder`` button to create an empty
+folder based on your project's name.
+
+Opening and importing projects
+------------------------------
+
+The next time you open the project manager, you'll see your new project in the
+list. Double click on it to open it in the editor.
+
+.. image:: img/editor_ui_intro_project_manager_06.png
+
+You can similarly import existing projects using the Import button. Locate the
+folder that contains the project or the ``project.godot`` file to import and
+edit it.
+
+.. image:: img/editor_ui_intro_project_manager_08.png
+
+When the folder path is correct, you'll see a green checkmark.
+
+.. image:: img/editor_ui_intro_project_manager_09.png
+
+Downloading demos and templates
+-------------------------------
+
+From the **Templates** tab you can download open source project templates and
+demos from the :ref:`Asset Library <doc_what_is_assetlib>` to help you get
+started faster.
+
+To download a demo or template:
+
+1. Click on its title.
+2. On the page that opens, click the download button.
+3. Once it finished downloading, click install and choose where you want to save
+   the project.
+
+.. image:: img/editor_ui_intro_project_manager_03.png