feat(build): change the default compilation target to ES2018 (Node.js…

… 10.x)

Now that we no longer support Node.js 8.x, we can configure TypeScript
compiler to emit code leveraging newer language constructs available
in Node.js 10.x.

See also 9424b40 which added support for ES2018/Node.js 10.x target
back in the days where we were producing custom `dist` versions
for each target Node.js version supported.

Signed-off-by: Miroslav Bajtoš <mbajtoss@gmail.com>

packages/build/config/tsconfig.common.json

@@ -16,7 +16,7 @@
     "module": "commonjs",
     "esModuleInterop": true,
     "moduleResolution": "node",
-    "target": "es2017",
+    "target": "es2018",
     "sourceMap": true,
     "declaration": true,
     "importHelpers": true