Increase workflow timeout

I've noticed that CI tests will hit the 15 minute timeout and fail. Perhaps we just need to increase the timeout?

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ on: [push, pull_request]
 jobs:
   Tests:
     runs-on: ${{ matrix.os }}
-    timeout-minutes: 15
+    timeout-minutes: 20
     strategy:
       matrix:
         node-version: [8, 10, 12, 14, 16]