Add dev flag to install command

[getJv]

Updates the composer require command to use --dev and avoid extra an extra prompt

Current state

The command in the docs generates the followng output:

/var/www/html/laravel-solutions $ composer require spatie/laravel-error-solutions
The package you required is recommended to be placed in require-dev (because it is tagged as "dev") but you did not use --dev.
Do you want to re-run the command with --dev? [yes]?

Proposal

Once the package is tagged as dev using the flag will prevent an extra user prompt

[riasvdv]

Thanks!