[gnome-builder] help: add link to api reference

[Christian Hergert <chergert src gnome org>]

commit b5c4aecbdcf2a40750b2b24ee52134e8bd7bfe05
Author: Christian Hergert <chergert redhat com>
Date:   Sun Nov 5 21:35:51 2017 -0800

    help: add link to api reference

 doc/help/plugins/apiref.rst |    6 ++++++
 doc/help/plugins/index.rst  |    1 +
 2 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/doc/help/plugins/apiref.rst b/doc/help/plugins/apiref.rst
new file mode 100644
index 0000000..527809f
--- /dev/null
+++ b/doc/help/plugins/apiref.rst
@@ -0,0 +1,6 @@
+#############
+API Reference
+#############
+
+You can find the Builder API reference for C at https://developer.gnome.org/libide/.
+
diff --git a/doc/help/plugins/index.rst b/doc/help/plugins/index.rst
index 6cf77a7..aa37f43 100644
--- a/doc/help/plugins/index.rst
+++ b/doc/help/plugins/index.rst
@@ -12,6 +12,7 @@ You may also chooser to implement extensions in C or Vala.
    :maxdepth: 3
    :titlesonly:
 
+   apiref
    enabling
    creating
    workbench/index