Added rules for "loading" spinner

Added rules for the “loading” spinner to position it and keep it hidden.
Updated path

Updated the reference path to remove leading slash.
Expanded script

Expanded script to send and receive requests.
Updated path

Updated path to remove the leading slash.
Fixed class description

Fixed class description to better explain its function
Fixed path

Updated path to remove the leading slash.
Localize script

Added call to localize the script that dynamically updates the author
info.
Added "loading" spinner

Added code to place “loading” spinnner next to dropdown menu.
JavaScript call will display it when needed.
Remove call for $wpdb

Remove the global designation for $wpdb (unneeded)
Retrieve nonce sent by JS

Retrieve the nonce from data sent by script.
Changed POST element

Changed the identifier of the POST to match the value sent by JavaScript
Check for nonce

Validate the nonce sent by JavaScript against the one stored by
WordPress. If invalid, end the script.
Moved entry

Entry is pushed down by new code above it. No changes to this code.
Permissions check

Check that the user’s permissions are sufficient to perform the
requested action.
Set values retrieved from database

Set the author info values retrieved from their profile to send back to
JavaScript.
Encode data as JSON

Encode the data to be sent back as JSON, and then send the response.
Changed 'die' to 'exit'

Changed ‘die’ to ‘exit’ purely as personal preference.
Renamed action hook

Renamed the action hook for easier use elsewhere in the code.
Image for "loading" spinner

Image to use for “loading” spinner.