Improve support for old browsers (#9515)

* FEATURE: Improve crawler view

* FIX: Make lazyYT crawler-friendly

* DEV: Rename discourse-internet-explorer to discourse-unsupported-browser

* DEV: Detect more unsupported browsers

Follow-up to 4eebbd2212.

* FIX: Hide browser update notice in print view

app/assets/javascripts/browser-detect.js

@@ -1,3 +1,12 @@
 if (!window.WeakMap || !window.Promise) {
   window.unsupportedBrowser = true;
+} else {
+  // Some implementations of `WeakMap.prototype.has` do not accept false
+  // values and Ember's `isClassicDecorator` sometimes does that (it only
+  // checks for `null` and `undefined`).
+  try {
+    new WeakMap().has(0);
+  } catch (err) {
+    window.unsupportedBrowser = true;
+  }
 }