Adds support for reading config/term-meta.json

[goodguyry]

This change makes the meta registration system more flexible by supporting both post and term meta configurations through a similar interface and shared code.

• Refactors the existing register_post_meta_from_defs() function into a more generic register_meta_from_defs() function that can handle both post and term meta
  • Adds a new register_term_meta_from_defs() function that uses the generic function with 'term' context
  • Updates the original register_post_meta_from_defs() to use the new generic function with 'post' context
• Updates plugin.php to call both registration functions

[kingkool68]

👍