[gnome-builder] doc: add blurb on coordinating plugins

[Christian Hergert <chergert src gnome org>]

commit 7ee57f5f56f481033a33b1f889b0ba3c7eed2f3f
Author: Christian Hergert <chergert redhat com>
Date:   Wed Sep 6 20:20:08 2017 -0700

    doc: add blurb on coordinating plugins

 doc/plugins/editor/view.rst |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/doc/plugins/editor/view.rst b/doc/plugins/editor/view.rst
index d2c47e2..a1e00df 100644
--- a/doc/plugins/editor/view.rst
+++ b/doc/plugins/editor/view.rst
@@ -61,3 +61,11 @@ In the example provided, the plugin interface would be enabled for ``C`` and ``C
        def do_stack_set(self, stack):
            print("View was moved to document stack", stack)
 
+           # If you have an Ide.LayoutStackAddin, you might want to coordinate
+           # between them. To locate your stack addin, you can fetch it like
+           # the following:
+           #
+           # Note that the module name must match Module= inyour .plugin file.
+           module_name = 'my-plugin-module'
+           other_addin = Ide.LayoutStackAddin.find_by_module_name(stack, module_name)
+