SDSS-1007: Add support for global footer variant.

[joegl]

READY FOR REVIEW

Summary

• In SDSS we use the "dark" variant for the Global Footer. We've had to hard-code this into an override in the page.html.twig file, because the option doesn't exist in the theme. This adds the option.

Review By (Date)

ASAP

Criticality

• How critical is this PR on a 1-10 scale? Also see Severity Assessment.
• E.g., it affects one site, or every site and product?

Urgency

• Med/high

Review Tasks

Setup tasks and/or behavior to test

1. Check out this branch
2. Rebuild Cache and import config drush cr ; drush ci
3. Verify global footer is red
4. Navigate to theme settings page: /admin/appearance/settings/sdss_subtheme
5. Change the Global Footer Variant from default to dark
6. Verify the global footer is now dark and not red (may have to flush/rebuild cache)

Site Configuration Sync

• Is there a config:export in this PR that changes the config sync directory? No

Front End Validation

• Design is approved by @ user?
• HTML validation: Is the markup using the appropriate semantic tags and passes validation? Or, QA request ticket created?
• Cross-browser testing: Has been performed? Or, QA request ticket created?
• Automated accessibility: Scans performed? Or, QA request ticket created?
• Manual accessibility: Manually tested? Or, QA request ticket created?

Backend / Functional Validation

Code

• Are the naming conventions following our standards?
• Does the code have sufficient inline comments?
• Is there anything in this code that would be hidden or hard to discover through the UI?
• Are there any code smells?
• Are tests provided? eg (unit, behat, or codeception)

Code security

• Are all forms properly sanitized?
• Any obvious security flaws or new areas for attack?

General

• Is there anything included in this PR that is not related to the problem it is trying to solve?
• Is the approach to the problem appropriate?

Affected Projects or Products

• Does this PR impact any particular projects, products, or modules?

Associated Issues and/or People

• JIRA ticket(s)
• Other PRs
• Any other contextual information that might be helpful (e.g., description of a bug that this PR fixes, new functionality that it adds, etc.)
• Anyone who should be notified? (@mention them here)

Resources

• AMP Tool
• Accessibility Manual Test Script
• HTML Validator
• Browserstack and link to Browserstack Credentials

[pookmish]

Just a couple small tweaks