adding injectTag utilities with its helpers

feel free to push back on these utils if you don't think they're necessary. I 'll update my dependency.

This PR along with this [spam-be-gone commit](
https://github.com/akhoury/nodebb-plugin-spam-be-gone/commit/971f0af6cdeca34547ea472fa147330c9f4fad2e) closes https://github.com/designcreateplay/NodeBB/issues/1548