Fix _load_textdomain_just_in_time notice

[aihowes]

Adds set_cloudinary_filters to the init hook.

Fixes #1038

Approach

• The i18n function __() was being called in the constructor of the class which is considered to early
• I have moved the relevant code to a separate function and added the function as an action to take place on init.

QA notes

• Detail the steps needed to verify the PR.