This commit introduces a Webpack configuration file that bundles the GUI
code along with its dependencies (except the Etcher SDK and its own
dependencies), and uses Babel to add support for JSX (required by the
Rendition library).
The GUI code that goes into the bundle was moved to `lib/gui/app` so we
can easily ignore the whole subdirectory when creating production
distributable packages.
We now have a new make target called `webpack` that can be used to
create the GUI bundle. Such target will be called everytime a package is
generated.
Change-Type: patch
Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>