Add prettier and re-configure lint according to current best practises

jest/__mocks__/intlMock.js

@@ -1,6 +1,6 @@
 /* eslint-env node */
-const path = require("path");
-const { transform } = require("../../webpack-utils/intl-loader");
+const path = require('path');
+const { transform } = require('../../webpack-utils/intl-loader');
 
 module.exports = {
   /**
@@ -9,14 +9,10 @@ module.exports = {
    * @param {{[key: string]: any}} config - jest config
    * @param {{instrument: boolean}} options - additional options
    *
-   * @return {string}
+   * @returns {string}
    */
   // eslint-disable-next-line no-unused-vars
   process(src, filename, config, options) {
-    return transform(
-      src,
-      filename,
-      path.resolve(`${__dirname}/../../..`)
-    );
-  }
+    return transform(src, filename, path.resolve(`${__dirname}/../../..`));
+  },
 };

jest/setupAfterEnv.js

@@ -5,19 +5,19 @@ import Adapter from 'enzyme-adapter-react-16';
 configure({ adapter: new Adapter() });
 
 if (!window.localStorage) {
-    window.localStorage = {
-        getItem(key) {
-            return this[key] || null;
-        },
-        setItem(key, value) {
-            this[key] = value;
-        },
-        removeItem(key) {
-            delete this[key];
-        }
-    };
+  window.localStorage = {
+    getItem(key) {
+      return this[key] || null;
+    },
+    setItem(key, value) {
+      this[key] = value;
+    },
+    removeItem(key) {
+      delete this[key];
+    },
+  };
 
-    window.sessionStorage = {
-        ...window.localStorage
-    };
+  window.sessionStorage = {
+    ...window.localStorage,
+  };
 }