Keep Google Analytics 4 at CacheStorage and loading with priority low

ga4-sandbox.js

            const GA = 'https://www.googletagmanager.com/gtag/js?id=GT-TQL9TSPB'
            
            caches.open('ga')
            .then(c =>
                c.match(GA)
                .then(r =>
                    r || fetch(GA, {priority: 'low'})
                    .then(r =>
                        r.ok && c.put(GA, r.clone()).then(_ => r)
                    )
                )
            )
            .then(r => r.text())
            .then(code => {
                const script = document.createElement('script')
                script.textContent = code
                document.head.appendChild(script)
                
                window.dataLayer = window.dataLayer || []
                window.gtag = function gtag(){dataLayer.push(arguments)}
                gtag('js', new Date())
                gtag('config', 'GT-TQL9TSPB')
            })