Re-roll yarn.lock.

Updates to the most recent allowed version of all dependencies.

Had to specify a resolution for `engine.io` because it dropped Node 6
support within the current major version. 😭

Author: Robert Jackson

package.json

@@ -42,6 +42,7 @@
   "devDependencies": {
     "body-parser": "^1.18.3",
     "broccoli-asset-rev": "^3.0.0",
+    "broccoli-file-creator": "^1.1.1",
     "broccoli-test-helper": "^1.5.0",
     "chai": "^4.1.2",
     "chai-fs": "^2.0.0",
@@ -75,8 +76,10 @@
     "release-it": "^12.0.1",
     "release-it-lerna-changelog": "^1.0.2",
     "request": "^2.88.0",
-    "rsvp": "^4.8.3",
-    "broccoli-file-creator": "^1.1.1"
+    "rsvp": "^4.8.3"
+  },
+  "resolutions": {
+    "**/engine.io": "~3.3.0"
   },
   "engines": {
     "node": "6.* || 8.* || >= 10.*"