Store allowlist of third-party plugins in a JSON file

From @edsummersnc:

> Consider refactoring the list of approved plugins into a JSON file or similar file type. Include npm package name, description, and repo. This will allow users of the scanner to find third-party plugins, perform their own security review, file issues on those plugins, contribute fixes, fork/extend, etc.

The allowlist is currently maintained in the repo's codebase, as it contains only a single entry.

Locate the current approved-plugin allowlist in the repository codebase and read how it is consumed. Move the list into a JSON file containing each npm package name, description, and repository, then verify the scanner still discovers the existing plugin from that file.

Written by the indexing model from the issue text.