fix: package.json, package-lock.json & .snyk to reduce vulnerabilities

The following vulnerabilities are fixed with a Snyk patch:
- https://snyk.io/vuln/SNYK-JS-TREEKILL-536781

Author: snyk-bot

.snyk

@@ -1,8 +1,11 @@
 # Snyk (https://snyk.io) policy file, patches or ignores known vulnerabilities.
-version: v1.13.5
+version: v1.14.0
 ignore: {}
 # patches apply the minimum changes required to fix a vulnerability
 patch:
   SNYK-JS-HTTPSPROXYAGENT-469131:
     - diff-dom > updates > make-fetch-happen > https-proxy-agent:
         patched: '2019-10-03T21:45:45.262Z'
+  SNYK-JS-TREEKILL-536781:
+    - snyk > snyk-sbt-plugin > tree-kill:
+        patched: '2019-12-11T21:43:10.020Z'