Add multi-compare for Confluence page versions

• As an end user, for document version control and compliance reasons, I need to be able to compare not just one version to another, but multiple versions of a Confluence page at the same time on the same modal.

Example:

• A Confluence Page, "Alpha", has 25 versions.
• As a user, I want to compare version 1 to versions 10, 11, 12, and 24 simultaneously.
• The expectation with this is that in the "Page History > Compare" page, all comparisons will show up.
• Currently, you can only compare one version to another (one-to-one compare).