Remove IE11 support from babel transpilation

We do not have a fully defined babel preset environment just yet, thus
we go with a bit of conservative values for the other browsers (support
for more versions than necessary) just in order to be safe and until we
have decided on the exact versions to support.

babel.config.js

@@ -9,8 +9,23 @@ let presets = [
       useBuiltIns: 'usage',
       corejs: { version: 3, proposals: true },
       modules: false,
+      /**
+       * This list of browsers is a conservative first definition, based on
+       * https://docs.gitlab.com/ee/install/requirements.html#supported-web-browsers
+       * with the following reasoning:
+       *
+       * - Edge: Pick the last two major version before the Chrome switch
+       * - Rest: We should support the latest ESR of Firefox: 68, because it used quite a lot.
+       *         For the rest, pick browser versions that have a similar age to Firefox 68.
+       *
+       * See also this follow-up epic:
+       * https://gitlab.com/groups/gitlab-org/-/epics/3957
+       */
       targets: {
-        ie: '11',
+        chrome: '73',
+        edge: '17',
+        firefox: '68',
+        safari: '12',
       },
     },
   ],

changelogs/unreleased/leipert-ie11-babel-preset-env.yml

+---
+title: Remove Internet Explorer 11 from babel transpilation
+merge_request: 36840
+author:
+type: removed