[META] Update CI Implementation

[kporras07]

Take inspiration from https://github.com/Lullabot/drupal8ci to update our CI implementation:

• Standardize to ahoy commands
• Document mailhog config
• Print domain in -url commands
• Add PHPUnit support (Add PHPUnit support #29)
• Evaluate adding other CI solution (travis, gitlab) (Evaluate adding other CI Solution #32)
• Add lighthouse (Add lighthouse #33)
• Add Visual Regression testing (Add visual regression testing #34)