[gnome-builder] doc: add basic debugger docs

[Christian Hergert <chergert src gnome org>]

commit 8b7c4d5da460159e81415af509c92a8ec5538b51
Author: Christian Hergert <chergert redhat com>
Date:   Sat Sep 2 23:50:25 2017 -0700

    doc: add basic debugger docs

 doc/figures/run-with-debugger.png |  Bin 0 -> 251736 bytes
 doc/projects/debugging.rst        |   28 +++++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletions(-)
---
diff --git a/doc/figures/run-with-debugger.png b/doc/figures/run-with-debugger.png
new file mode 100644
index 0000000..ac88bf8
Binary files /dev/null and b/doc/figures/run-with-debugger.png differ
diff --git a/doc/projects/debugging.rst b/doc/projects/debugging.rst
index 0812e81..3ddd09c 100644
--- a/doc/projects/debugging.rst
+++ b/doc/projects/debugging.rst
@@ -2,5 +2,31 @@
 Debugging your Project
 ######################
 
-.. warning:: Builder does not currently support debugging, but it is expected in version 3.26.
+Builder provides a debugger interface which can be extended for various languages.
+Currently, there is support for the GNU Debugger which supports C, C++, and to some degree Rust, and Vala.
+
+To start the debugger, select "Run with Debugger" from the Run button.
+
+.. image:: ../figures/run-button.png
+   :width: 322 px
+   :align: center
+
+.. warning:: If Builder fails to locate a debugger that is compatible with your project, an error message 
will be displayed.
+
+After Builder has started the debugger, you'll be greeted with a series of controls to step through your 
application.
+
+.. image:: ../figures/run-with-debugger.png
+   :width: 1142 px
+   :align: center
+
+.. note:: The debugger support in Builder is currently limited, and will be expanded in future releases.
+
+You can currently do a few things with the debugger in Builder.
+
+ - Step through execution in a variety of fashions
+ - Browse threads and thread stacks
+ - Explore current register values
+ - View the values of locals and parameters
+ - Add and remove breakpoints to aid in stepping through execution
+ - View disassembly when no source is available