docs: Added Window Management Fiddle example (#20535)

docs/fiddles/windows/manage-windows/frameless-window/renderer.js

@@ -0,0 +1,25 @@
+const { BrowserWindow } = require('electron').remote
+const shell = require('electron').shell
+
+const framelessWindowBtn = document.getElementById('frameless-window')
+
+const links = document.querySelectorAll('a[href]')
+
+framelessWindowBtn.addEventListener('click', (event) => {
+  const modalPath = 'https://electronjs.org'
+  let win = new BrowserWindow({ frame: false })
+
+  win.on('close', () => { win = null })
+  win.loadURL(modalPath)
+  win.show()
+})
+
+Array.prototype.forEach.call(links, (link) => {
+  const url = link.getAttribute('href')
+  if (url.indexOf('http') === 0) {
+    link.addEventListener('click', (e) => {
+      e.preventDefault()
+      shell.openExternal(url)
+    })
+  }
+})