Fix 'prevent-element-src-loading' — TrustedScriptURL is not defined in Firefox

[AdamWr]

TrustedScriptURL is not defined in Firefox and scriptlet does not work correctly.

Steps to reproduce:

1. Add to user rules:

example.org#%#//scriptlet('prevent-element-src-loading', 'script', 'test.js')

2. Go to - https://example.org/
3. Open devtools and run in console:

(() => {
    const script = document.createElement('script');
    script.src = 'test.js';
    document.body.appendChild(script);
})();

There is an error: Uncaught ReferenceError: TrustedScriptURL is not defined.

Screenshot

The problem seems to be here:

Scriptlets/src/scriptlets/prevent-element-src-loading.js

Line 135 in 938bbe3

if (policy && urlValue instanceof TrustedScriptURL) {

TrustedScriptURL is undefined and urlValue instanceof TrustedScriptURL throws error.
I guess we can change it to:

if (policy && policy.isSupported && urlValue instanceof TrustedScriptURL) {