🏗 Antora: Create `policy` module

This commit introduces a new Antora module for all Mindshare Committee policies and bylaws. Right now, we do not have many, just the event report policy. In this commit, I migrated the existing event report policy into this new module, updated some broken xrefs, added the ROOT partials for using common {shortcodes}, and other minor formatting.

The definition and interpretation of the policy were not altered, so I am going to merge this commit directly to main. Setting this up now sets the path for documenting future Mindshare Committee policies and bylaws more easily (e.g. social media management).