Allow use_local_engine to use local network addresses like 192.168.*.*

[yaustar]

Private network address ranges are standardised to certain ranges: https://whatismyipaddress.com/private-ip

Having this will make engine development with the Editor with devices like XR headsets and phones a lot easier

[kungfooman]

Quick snippet to test if an URL is in a private network that can be quickly iterated in devtools:

console.clear();
// Alternatively, but regex seems more complex:
// https://stackoverflow.com/questions/5284147/validating-ipv4-addresses-with-regexp
function isIP(str) {
    const parts = str.split(".");
    if (parts.length != 4) {
        return false;
    }
    const nums = parts.map(part => parseInt(part));
    return nums.every(num => num >= 0 && num <= 255);
}
function isPrivate(url_) {
    const { host } = new URL(url_);
    if (host === 'localhost' || host === '127.0.0.1') {
        return true;
    }
    if (isIP(host)) {
        if (host.startsWith("192.168.") || host.startsWith("10.")) {
            return true;
        }
        if (host.startsWith("172.")) {
            const second = parseInt(host.split('.')[1]);
            return second >= 16 && second <= 31;
        }
    }
    return false;
}
const tests = [
    // private:
    "http://10.0.1.2/playcanvas-engine/src/index.js",
    "http://127.0.0.1/playcanvas-engine/src/index.js",
    "http://172.16.1.2/playcanvas-engine/src/index.js",
    "http://172.31.1.2/playcanvas-engine/src/index.js",
    "http://localhost/playcanvas-engine/src/index.js",
    // NOT private:
    "http://localhostfake.com/playcanvas-engine/src/index.js",
    "http://9.0.1.2/playcanvas-engine/src/index.js",
    "http://172.15.1.2/playcanvas-engine/src/index.js",
    "http://172.32.1.2/playcanvas-engine/src/index.js",
    "http://192.168.0.1.xss.com/playcanvas-engine/src/index.js"
];
tests.forEach(_ => console.log(isPrivate(_) ? "private" : "NOT private", '=', _));

Output:

private = http://10.0.1.2/playcanvas-engine/src/index.js
private = http://127.0.0.1/playcanvas-engine/src/index.js
private = http://172.16.1.2/playcanvas-engine/src/index.js
private = http://172.31.1.2/playcanvas-engine/src/index.js
private = http://localhost/playcanvas-engine/src/index.js
NOT private = http://localhostfake.com/playcanvas-engine/src/index.js
NOT private = http://9.0.1.2/playcanvas-engine/src/index.js
NOT private = http://172.15.1.2/playcanvas-engine/src/index.js
NOT private = http://172.32.1.2/playcanvas-engine/src/index.js
NOT private = http://192.168.0.1.xss.com/playcanvas-engine/src/index.js

Edit: fix "IP" hiding as subdomain of xss.com by testing if it's actually an IP.