implemented frontend including separate message system; started to implement backend

yjs-poll/node_modules/isomorphic.js/browser.mjs

@@ -0,0 +1,25 @@
+/* eslint-env browser */
+export const performance = typeof window === 'undefined' ? null : (typeof window.performance !== 'undefined' && window.performance) || null
+
+const isoCrypto = typeof crypto === 'undefined' ? null : crypto
+
+/**
+ * @type {function(number):ArrayBuffer}
+ */
+export const cryptoRandomBuffer = isoCrypto !== null
+  ? len => {
+    // browser
+    const buf = new ArrayBuffer(len)
+    const arr = new Uint8Array(buf)
+    isoCrypto.getRandomValues(arr)
+    return buf
+  }
+  : len => {
+    // polyfill
+    const buf = new ArrayBuffer(len)
+    const arr = new Uint8Array(buf)
+    for (let i = 0; i < len; i++) {
+      arr[i] = Math.ceil((Math.random() * 0xFFFFFFFF) >>> 0)
+    }
+    return buf
+  }