doc: Convert Chromium OS docs to rst

Move this documentation over to reST. Move the example files into a files/
directory so they are still separate.

Do a few minor updates while we are here:
- Tidy up sandbox build instructions
- Update my github account name
- Add some talks and links

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/index.rst b/doc/index.rst
index f7aada9..02de1d4 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -87,6 +87,14 @@
 
    android/index
 
+Chromium OS-specific doc
+------------------------
+
+.. toctree::
+   :maxdepth: 2
+
+   chromium/index
+
 Indices and tables
 ==================