Revert "remove coverage threshold"

This reverts commit fc201da.

package.json

@@ -75,6 +75,14 @@
   },
   "jest": {
     "testEnvironment": "node",
+    "coverageThreshold": {
+      "global": {
+        "branches": 100,
+        "functions": 100,
+        "lines": 100,
+        "statements": 100
+      }
+    },
     "watchPlugins": [
       "jest-watch-typeahead/filename",
       "jest-watch-typeahead/testname"