Removed support for IE totally.

Added error message displayed in IE.

src/index.tsx

@@ -1,12 +1,10 @@
-import 'react-app-polyfill/ie11';
-import 'string.prototype.startswith';
-import 'array.prototype.find';
 import * as locale_en from 'react-intl/locale-data/en';
 import * as locale_pl from 'react-intl/locale-data/pl';
 import * as React from 'react';
 import * as ReactDOM from 'react-dom';
 import messages_pl from './translations/pl.json';
 import {addLocaleData} from 'react-intl';
+import {detect} from 'detect-browser';
 import {ChartView} from './chart_view';
 import {HashRouter as Router, Route, Switch} from 'react-router-dom';
 import {IntlProvider} from 'react-intl';
@@ -22,17 +20,29 @@ const messages = {
 };
 const language = navigator.language && navigator.language.split(/[-_]/)[0];
 
-ReactDOM.render(
-  <IntlProvider locale={language} messages={messages[language]}>
-    <Router>
-      <div className="root">
-        <Route component={TopBar} />
-        <Switch>
-          <Route exact path="/" component={Intro} />
-          <Route exact path="/view" component={ChartView} />
-        </Switch>
-      </div>
-    </Router>
-  </IntlProvider>,
-  document.querySelector('#root'),
-);
+const browser = detect();
+
+if (browser && browser.name === 'ie') {
+  ReactDOM.render(
+    <p>
+      Topola Genealogy Viewer does not support Internet Explorer. Please try a
+      different browser.
+    </p>,
+    document.querySelector('#root'),
+  );
+} else {
+  ReactDOM.render(
+    <IntlProvider locale={language} messages={messages[language]}>
+      <Router>
+        <div className="root">
+          <Route component={TopBar} />
+          <Switch>
+            <Route exact path="/" component={Intro} />
+            <Route exact path="/view" component={ChartView} />
+          </Switch>
+        </div>
+      </Router>
+    </IntlProvider>,
+    document.querySelector('#root'),
+  );
+}