docs/website: New website

This patch introduces a new buildroot website based on a modern flat
layout inspired by material design.

Each page of the old website is converted to the new css/layout, the
big bump is in main page which is completely rewritten. Content of
the old website is copied more or less verbatim, planning to add more
content in the future.

Signed-off-by: Angelo Compagnucci <angelo.compagnucci@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/website/images/clippy.svg

@@ -0,0 +1,3 @@
+<svg height="1024" width="896" xmlns="http://www.w3.org/2000/svg">
+  <path d="M128 768h256v64H128v-64z m320-384H128v64h320v-64z m128 192V448L384 640l192 192V704h320V576H576z m-288-64H128v64h160v-64zM128 704h160v-64H128v64z m576 64h64v128c-1 18-7 33-19 45s-27 18-45 19H64c-35 0-64-29-64-64V192c0-35 29-64 64-64h192C256 57 313 0 384 0s128 57 128 128h192c35 0 64 29 64 64v320h-64V320H64v576h640V768zM128 256h512c0-35-29-64-64-64h-64c-35 0-64-29-64-64s-29-64-64-64-64 29-64 64-29 64-64 64h-64c-35 0-64 29-64 64z"/>
+</svg>