build(tsconfig-json): include es2019 in libs to have Array#flat()

With this we no longer need to include lodash for flattening 2D arrays
which is great when
optimizing for bundle sizes in the browser builds.

Signed-off-by: Peter Somogyvari <peter.somogyvari@accenture.com>

tsconfig.json

@@ -8,6 +8,7 @@
       "es2015",
       "es2016",
       "es2017",
+      "es2019",
       "dom"
     ], /* Specify library files to be included in the compilation. */
     // "allowJs": true,                       /* Allow javascript files to be compiled. */