ELKS has now its own CI

["Marc-F. Lucca-Daniau" <mfld.fr@xxxxxxxxx>]

Hello all,

ELKS project has now its own Continuous Integration (CI) : 
https://github.com/elks-org/elks/actions

The cross tools are pre-built in a distinct workflow to save time, and 
the archive of that pre-build is available as an artifact for the Ubuntu 
users.

The main build works for now on the default configuration, and the 
resulting 'FD1440.bin' image is also available as an artifact for all 
users to be able to test without building ELKS.

Enjoy !

MFLD