Add ability to specify a location for includes

[rodrigoaguilera]

Currently I have this configuration:

"drupal-scaffold": {
            "initial": {
                ".editorconfig": "../.editorconfig",
                ".gitattributes": "../.gitattributes"
            },
...
        },

And it works great except for the little thing about the "initial" files still living in the repo under /web. What I really wanted to do is moving them.

I think this can be solved with two different ways

• The "include" config allows a keyed array (I do not know the name in JSON) with source and destination and treating those entries with only a value as usual

• Add an "move" config that also places the scaffolded files to a different location.

Related issues:
#54
drupal-composer/drupal-project#220