Add favicon for the documentation html

Import the favicon from https://www.yoctoproject.org/, convert it to
16x16 (as per the Sphinx documentation) to make a 1291B image of the
Yocto logo.

(From yocto-docs rev: 73119a723b48a4038479591f0443c5acb3d21337)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
(cherry picked from commit e3ee43e6d70685a2404aae2d60557a42879b0bb1)
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

documentation/conf.py

@@ -136,6 +136,7 @@ except ImportError:
     sys.exit(1)
 
 html_logo = 'sphinx-static/YoctoProject_Logo_RGB.jpg'
+html_favicon = 'sphinx-static/favicon.ico'
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,