clarify composer installation docs page

[arhimede]

dotkernel/frontend#433

Default is 0 or 1 ?
Should we add a warning to always run composer commands from CLI ?

for instance, PhpStorm button "composer install" runss with no interactions

[alexmerlin]

As I mentioned a couple of days ago, during our daily TSC meeting, since this commit DotKernel API does not ask in which file you want to inject *ConfigProvider into.
This was the solution for an issue we encountered when composer installing the dependencies by automated tools in non-interactive mode (if I remember correctly) did not install dev packages.

At that time, I also mentioned that in long term it might not be the best solution and we might revert those changes.

Also, see my dotkernel/frontend#433 (comment)