#41 theme variables

[alxp]

What does this Pull Request do?

• Related GitHub Issue: Add more Mirador configuration keys as theme variables. #41

What's new?

This change adds three new theme variables, and hooks them up to the block class configuration.

• window_config
• • workspace_config
• • thumbnail_navigation_position
    The first two are arrays and can pass along any configs to the Mirador instantiation JS code to, e.g., remove unwanted UI elements.

• Does this change add any new dependencies? No
• Does this change require any other modifications to be made to the repository
  (i.e. Regeneration activity, etc.)? No
• Could this change impact execution of existing code? No

How should this be tested?

After clearing cache, this can be tested by implementing the example hook or block instantiation from the updated README and verifying that Mirador's appearance changes accordingly.

Documentation Status

• Does this change existing behaviour that's currently documented? No
• Does this change require new pages or sections of documentation? README updated.
• Who does this need to be documented for? Developers.

Interested parties

Tag (@ mention) interested parties or, if unsure, @Islandora/committers