Added equiv search documentation merged into main

[ekansa]

brief description of changes

This implements the approved PR already merged onto the master branch onto this release branch

issues addressed

https://github.com/archesproject/arches-docs/issues/225

further comments

I'll cherry pick this change for the other v7, v6, and v5 branches

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This box must be checked

• [x] the PR branch was originally made from the base branch

This box should be checked

• [x] after these changes the docs build locally without error

This box should only be checked you intend to follow through on it (we can do it on our end too)

• [x] I will cherry-pick all commits in this PR into other branches that should have them after this PR is merged