Add `@types/chai`

package.json

@@ -92,6 +92,7 @@
     "websocket": "^1.0.25"
   },
   "devDependencies": {
+    "@types/chai": "^4.1.2",
     "@types/lodash": "^4.14.106",
     "@types/qs": "^6.5.1",
     "@types/react": "^16.3.1",

yarn.lock

@@ -36,6 +36,10 @@
   dependencies:
     samsam "1.3.0"
 
+"@types/chai@^4.1.2":
+  version "4.1.2"
+  resolved "https://registry.yarnpkg.com/@types/chai/-/chai-4.1.2.tgz#f1af664769cfb50af805431c407425ed619daa21"
+
 "@types/lodash@^4.14.106":
   version "4.14.106"
   resolved "https://registry.yarnpkg.com/@types/lodash/-/lodash-4.14.106.tgz#6093e9a02aa567ddecfe9afadca89e53e5dce4dd"