Specify Node 10 as the Babel target

Preserve generator syntax instead of adding regeneratorRuntime
dependency to transpiled output.

Fix #9.

Author: wimpyprogrammer

src/.babelrc

@@ -1,4 +1,14 @@
 {
-	"presets": ["@babel/typescript", "@babel/env"],
+	"presets": [
+		"@babel/typescript",
+		[
+			"@babel/preset-env",
+			{
+				"targets": {
+					"node": "10"
+				}
+			}
+		]
+	],
 	"plugins": ["@babel/plugin-proposal-class-properties"]
 }