Make sure documentation (and Quick Start guide) are up to date

[geerlingguy]

After the major changeover from Drush make to Composer defaults for building the Drupal site, we need to make a pass through the docs and ensure they're correct for both use cases.

See:

• Default to Composer-based site building instead of Drush Make #699
• Use of Composer (instead of Drush Make) for building Drupal site #506

Also, as I'm going to include necessary vagrant-cachier configuration by default per #702, we need to update the docs relating to that config in the Composer guilde.

cc @oxyc — I'll try to take a pass tonight after finishing up more testing, then if you want to glance through, that would be much appreciated!

[oxyc]

I'm signing off for tonight but I can have a look tomorrow. This is going to be another awesome release!

[geerlingguy]

Working on this now.

[oxyc]

I've got a few additions I can add once you're done.

Eg change the composer create-project docs to use acquia/lightning-project as an example:

drupal_composer_project_package: "acquia/lightning-project:^8.1.0"
drupal_composer_project_options: "--prefer-dist --stability rc --no-interaction"
drupal_core_path: "{{ drupal_composer_install_dir }}/docroot"

[geerlingguy]

@oxyc - You can add them in now; I'm finished with my first pass!

[geerlingguy]

I think we're good now.