xF2 Add-on [MMO] Old Thread Warning 2.3.0 Beta 1

Support 2.3.0
Update js code (thx @NikitOS)

In threads, the warning is now displayed in a human-readable form
Added new options:

• Displays short format of time units
• Date diff options

Min php 7.1

A warning about old threads is now displayed in the editor itself before the reply button.
Minimum version of XF is now 2.2.0