Logout and delete data when user logs out of WordPress

[psrpinto]

Fixes #118

Previously, before the move to using hydrogen internally instead of chatterbox, we implemented logging the user out from chatrix when they are not logged in to WordPress. This code was non-functional since the move to hydrogen.

The approach we took was to execute some JavaScript on all non-logged-in page loads. However, this approach prevents chatrix from being used without logging in to WordPress, since the user would be logged out from chatrix on every page load. Instead, the user should be logged out from chatrix only if a WordPress logout has happened.

That's the approach we take in this PR. We set a cookie on WordPress logout, then run some JavaScript if and only if that cookie exists. This allows for using chatrix without logging in to WordPress. Chatrix logout will still happen if the user subsequently logs in and out of WordPress.

Sumary of changes

• (The two first commits are unrelated to this PR, just fixing little things I noticed)
• Move logout-related JavaScript code from src/ to frontend/, and add a vite build for this which produces a logout.iife.js bundle. This allows us to use TypeScript instead of vanilla JS.
• Enqueue logout.iife.js on all non-logged-in page loads
• Set a chatrix-logout cookie on WordPress logout
• In logout.ts, check it chatrix-logout cookie exists. If it does exist, logout all chatrix sessions, then delete all data in local storage and indexedDB.

[ashfame]

Works well! 👏

I am curious if you ran into the need to load the logout JS code all the time as opposed to only doing it when the logout cookie is detected, as you wanted to do earlier?

[psrpinto]

That's a good point about only loading the logout JS when the cookie is detected, didn't even cross my mind. (Previously I mentioned only loading the logout JS code when needed, but I think that was before we settled on using a cookie.) I will look into this in another PR.