[DOCS] Add more details about flow

Author: jaapio

docs/architecture.rst

@@ -24,3 +24,24 @@ all components.
 The ``guides``, ``guides-markdown`` and ``guides-restructuredtext`` are seen as the main
 libaries of the project. The other components are optional and can be used to extend the
 functionality of the main libraries for specific use cases.
+
+Application flow
+================
+
+Processing documents is done in a few steps.
+
+#. :php:class:`Parsing <\phpDocumentor\Guides\Parser>` The first step is to parse the document. This is done by the :doc:`parser` component. The
+   parser component will parse the document and create a tree of nodes. Each node
+   represents a part of the document. For example a paragraph, a list or a table.
+#. :php:class:`Compiling <\phpDocumentor\Guides\Compiler\Compiler>` The second step is to compile the tree of nodes. This is done by the :doc:`compiler`
+   component. During the compilation modifications can be made to the tree of nodes. For
+   example the compiler can add a table of contents to the tree of nodes.
+
+#. :php:class:`Rendering <\phpDocumentor\Guides\Renderer\BaseTypeRenderer>` The third step is to render the tree of nodes. This is done by the :doc:`render`
+   component. The render component will render the tree of nodes to a specific output
+   format. By default twig templates are used to render nodes to HTML. But you can
+   create your own templates to render nodes to other formats. Or implement your own
+   renderer to use a different template engine.
+
+.. uml:: _uml/application-flow.puml
+    :caption: Application flow

docs/developers/index.rst

@@ -8,5 +8,7 @@ application to render ReStructuredText or Markdown documents. Or want to integra
 it in some other way that is not possible with the ``guides`` command line tool.
 
 .. toctree::
+   :maxdepth: 1
+   :titlesonly:
 
    extensions/index

docs/index.rst

@@ -1,7 +1,5 @@
 ..  include:: /include.rst.txt
 
-:project:
-    Guides
 :version:
     dev-main
 
@@ -49,4 +47,5 @@ If you are looking for a complete solution to create a documentation website the
     developers/index
     architecture
     reference/index
+    contributions/index
     about