fix manifest v3 issue

[nikkiBot]

Manifest v2 is now deprecated, and thus the shift to v3 was needed

[optimisan]

Great, I was just working on this

[optimisan]

Just a few suggestions, I will appreciate if you take a look!

[optimisan]

Are you sure you need all these?

Only csp.js is working for me.

[optimisan]

Refactor content.ts

Since csp.js is a separate file, I think content.ts is doing too many things.

We can remove this disabling business out of content.ts and keep this as a content script instead of injecting.

csp.js will inject the code instead, which can be something like this:

const disablingCode = ```$('#sortable_nav').sortable('destroy');
$('#sortable_nav').enableSelection();
```
const script = document.createElement('script');
script.textContent = disablingCode;
(document.head || document.documentElement).appendChild(script);

[optimisan]

This should be a separate pull request though.

[optimisan]

The default_icon key is recommended here (which is basically a copy-paste from the icons above).

Also, you can add a default_title here that is shown as a tooltip on hover:

"action": {
		"default_icon": {
			"32": "icon.png",
			"48": "icon.png",
			"64": "icon.png",
			"128": "icon.png"
		},
		"default_title": "Click to run PS-Extender"
	}