How to password-protect content in Jekyll / GithubPages

function normalizeUrl(url) {
    if (url && url.match && url.match(/^https?:\/\//)) {
        return new URL(url).pathname
    } else {
        return url
    }
}

async function sponsorDecode(user, pass) {
    if (user !== "" && pass !== "") {
        const url = `/${user}-${sha256(pass)}.json`;
        const file = await fetch(url);
        const json = await file.json();
        const normalizedMap = {};

        for (const [key, value] of Object.entries(json)) {
            normalizedMap[normalizeUrl(key)] = normalizeUrl(value);
        }
        window.sponsorMap = normalizedMap;
        dispatchEvent(new Event("SPONSOR_INIT"))
    }
    //console.warn("SPONSOR!", window.sponsorMap)
}

async function sponsorInit() {
    await sponsorDecode(localStorage.getItem("sponsorUser") || "", localStorage.getItem("sponsorPass") || "");
}

async function sponsorLogin(user, pass) {
    try {
        localStorage.setItem("sponsorUser", user);
        localStorage.setItem("sponsorPass", pass);
        await sponsorInit();
        return true;
    } catch (e) {
        alert("Password error");
        return false;
    }
}

async function formSponsorLogin() {
    const userNode = document.querySelector('#sponsor-user');
    const passNode = document.querySelector('#sponsor-pass');
    if (!await sponsorLogin(userNode.value, passNode.value)) {
        userNode.value = "";
        passNode.value = "";
        userNode.focus();
    }
}

async function sponsorLogout() {
    localStorage.removeItem("sponsorUser");
    localStorage.removeItem("sponsorPass");
    document.location.reload();
}

window.sponsorMap = {};

let setSponsoredContent = false;

async function updateSponsor() {
    if (!setSponsoredContent) {
        const newUrl = window.sponsorMap[document.location.pathname];
        if (newUrl) {
            setSponsoredContent = true;
            const url = await fetch(newUrl);
            const html = await url.text();
            const parser = new DOMParser();
            const node = parser.parseFromString(html, "text/html");
            document.querySelector("#actual-post-content").appendChild(node.querySelector("#actual-post-content"));
            document.querySelector("#sponsor-content").innerHTML = node.querySelector("#sponsor-content").innerHTML;
            //postContentThis.innerHTML = postContent.innerHTML;
            //console.warn(newUrl);
            //console.warn(postContent)
        }
    }
}

function registerSponsor() {
    addEventListener("SPONSOR_INIT", () => {
        //console.warn("SPONSOR_INIT");
        updateSponsor();
    });

    updateSponsor();
}

sponsorInit();