Add pwa support

Tesses.YouTubeDownloader.Server/res/offline.js

@@ -0,0 +1,54 @@
+function addOffline(url,res)
+{
+    var videos = JSON.parse(localStorage.getItem("videos") ?? "[]");
+    videos.push({
+        url: url,
+        res: res
+    });
+    localStorage.setItem('videos',JSON.stringify(videos));
+}
+
+async function syncOffline()
+{
+    const json = localStorage.getItem("videos") ?? "[]";
+    if(json !== "[]")
+    {
+        const resp = await fetch('/api/v1/add',{
+            body: json,
+            headers: {
+                'Content-Type': 'application/json'
+            },
+            method: "POST"
+        });
+        if(resp.ok)
+        {
+            localStorage.removeItem('videos');
+        }
+    }
+}
+
+if(navigator.online)
+{
+    syncOffline();
+}
+
+window.addEventListener('online',()=>{
+    syncOffline();
+});
+
+async function getPersonalTempLink()
+{
+    const searchParams = new URLSearchParams(window.location.search);
+    const ent = searchParams.get("name");
+    if(ent)
+    {
+        const resp=await fetch(`./api/v1/personal_tmp_link?name=${encodeURIComponent(ent)}`);
+        if(resp.ok)
+        {
+            const text = await resp.text();
+            the_playlist_url.innerText = text;
+            the_playlist_url.href = text;
+            ui("#dialog");
+        }
+    }
+}