deps/jest: Add jsdom-global to dev dependencies

For a later test, we'll want to be able to set up the test environment
to appear as though it's a browser at a specified URL. Jest currently
uses `jsdom` as its mock-browser environment, but doesn't (presently)
expose the `jsdom` facilities needed to set the mock `location`. (See
jestjs/jest#5124.)

Fortunately, Jest does allow alternate mock environments. We install
one which is identical to Jest's default environment, except that it
does expose that capability.

package.json

@@ -104,6 +104,8 @@
     "flow-typed": "^2.4.0",
     "jest": "^24.9.0",
     "jest-cli": "^24.9.0",
+    "jest-environment-jsdom": "^24.9.0",
+    "jest-environment-jsdom-global": "^1.2.0",
     "jest-extended": "^0.11.2",
     "metro-react-native-babel-preset": "^0.54.1",
     "prettier": "^1.18.2",

yarn.lock

@@ -4737,6 +4737,11 @@ jest-each@^24.9.0:
     jest-util "^24.9.0"
     pretty-format "^24.9.0"
 
+jest-environment-jsdom-global@^1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/jest-environment-jsdom-global/-/jest-environment-jsdom-global-1.2.0.tgz#dd5b16fe0a0566ee40010d8632be5adf5a5ccb65"
+  integrity sha512-41cDl0OxzmFY/cnW0COUN+lnt2N2ks1r3V4fAKOnlZ9xIrGy0PNPan+Bz8HP+uQy/8bGV6T7J4Oi7X+h43It6g==
+
 jest-environment-jsdom@^24.9.0:
   version "24.9.0"
   resolved "https://registry.yarnpkg.com/jest-environment-jsdom/-/jest-environment-jsdom-24.9.0.tgz#4b0806c7fc94f95edb369a69cc2778eec2b7375b"