[gnome-builder] docs: start on creating a plugin documentation

[Christian Hergert <chergert src gnome org>]

commit a34fe81e69fd31a92b01af90cdb728aa6c0f8677
Author: Christian Hergert <chergert redhat com>
Date:   Wed Feb 22 01:08:01 2017 -0800

    docs: start on creating a plugin documentation

 doc/plugins/creating.rst |   70 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 70 insertions(+), 0 deletions(-)
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diff --git a/doc/plugins/creating.rst b/doc/plugins/creating.rst
index 1c46939..da5ff6c 100644
--- a/doc/plugins/creating.rst
+++ b/doc/plugins/creating.rst
@@ -1,3 +1,73 @@
 ##########################
 Creating Your First Plugin
 ##########################
+
+Plugins consist of two things.
+First, a meta-data file describing the plugin which includes things like a name, the author, and where to 
find the plugin.
+Second, the plugin code which can take the form of a shared library or python module.
+
+Builder supports writing plugins in C, C++, Vala, or Python.
+We will be using Python for our examples in this tutorial because it is both succinct and easy to get 
started with.
+
+First, we will look at our plugin meta-data file.
+The file should have the file-suffix of ".plugin" and it's format is familiar.
+It starts with a line containing "[Plugin]" indicating this is plugin meta-data.
+Then it is followed by a series of "Key=Value" key-pairs.
+
+.. code-block:: ini
+
+   # my_plugin.plugin
+   [Plugin]
+   Name=My Plugin
+   Loader=python3
+   Module=my_plugin
+   Author=Angela Avery
+
+Now we can create a simple plugin that will print "hello" when Builder starts and "goodbye" when Builder 
exits.
+
+.. code-block:: python3
+
+   # my_plugin.py
+
+   import gi
+
+   from gi.repository import GObject
+   from gi.repository import Ide
+
+   class MyAppAddin(GObject.Object, Ide.ApplicationAddin):
+
+       def do_load(self, application):
+           print("hello")
+
+       def do_unload(self, application):
+           print("goodbye")
+
+In the python file above, we define a new extension called ``MyAppAddin``.
+It inherits from ``GObject.Object`` (which is our base object) and implements the interface 
``Ide.ApplicationAddin``.
+We wont get too much into objects and interfaces here, but the plugin manager uses this information to 
determine when and how to load our extension.
+
+The ``Ide.ApplicationAddin`` requires that two methods are implemented.
+The first is called ``do_load`` and is executed when the extension should load.
+And the second is called ``do_unload`` and is executed when the plugin should cleanup after itself.
+Each of the two functions take a parameter called ``application`` which is an ``Ide.Application`` instance.
+
+Loading our Plugin
+==================
+
+Now place the two files in ``~/.local/share/gnome-builder/plugins`` as ``my_plugin.plugin`` and 
``my_plugin.py``.
+If we run Builder from the command line, we should see the output from our plugin!
+
+.. code-block:: sh
+
+   [angela@localhost ~] gnome-builder
+   hello
+
+Now if we close the window, we should see that our plugin was unloaded.
+
+.. code-block:: sh
+
+   [angela@localhost ~] gnome-builder
+   hello
+   goodbye
+
+Next, continue on to learn about other interfaces you can implement in Builder to extend it's features!