Issue/827 10.8.0 drupal docs

[Jwaxo]

Updates issue #827

Issue Description

Adds a readme for how to install the app for Drupal 8 usage, which resolves some of Issue #827

Summary of Changes

• Moves the Drupal theme files located in apps/drupal/theme to a subfolder, so that it matches the setup in apps/drupal/module.
• Adds instructions on how to use the files within the apps/drupal folder to set up a Drupal installation of Particle. If anything here is erroneous, feel free to update, and please tell me so that I can fix my own installation.

Additionally, this issue queue references a nonexistent develop branch.

[jryanconklin]

I hesitate to add the Drupal theme pieces a further directory down in apps since "decoupled" Particle might not be the default approach for some projects. Original intent being you'd completely move that directory and rename if you did intend to decouple.

That said, if you feel strongly about it I understand. You will need to update the dist paths in Drupal's yml files (info.yml and libraries).

[illepic]

Possible idea to get out of depth-a-palooza. :

- apps
-- drupal
--- particle_helper_module
---- particle_helper.info.yml, module stuff
--- particle_theme
---- particle.info.yml, theme files
--- particle_assets
---- index.js, webpack, eslint, etc

What do yall think?