* Simplify project files
* alire.toml: release set external for build mode
Default is already in the project file.

* alire.toml: fix build mode external name
Co-authored-by: Fabien Chouteau <chouteau@adacore.com>

* Formatted to 80 characters line width.

Revert "Revert "* Attempt to see if Github recognizes a README file also if it's in the github directory.""

This reverts commit f3887c8a.

This reverts commit 373276e1.

Added all kind of information and usage examples.