feat: Set ES6 as target and require Node >= 10.9 (#105)

BREAKING CHANGE: Node.js >= 10.9 is required.

Author: ffflorian

package.json

@@ -26,6 +26,9 @@
     "tslint-plugin-prettier": "2.0.1",
     "typescript": "3.5.3"
   },
+  "engines": {
+    "node": ">= 10.9"
+  },
   "files": [
     "dist"
   ],

tsconfig.json

@@ -3,7 +3,7 @@
     "alwaysStrict": true,
     "declaration": true,
     "forceConsistentCasingInFileNames": true,
-    "lib": ["dom", "esnext"],
+    "lib": ["esnext"],
     "module": "commonjs",
     "moduleResolution": "node",
     "noEmitOnError": true,
@@ -16,7 +16,7 @@
     "sourceMap": true,
     "strict": true,
     "strictFunctionTypes": true,
-    "target": "es5"
+    "target": "es6"
   },
   "exclude": ["dist", "node_modules", "spec"]
 }

yarn.lock

@@ -234,7 +234,7 @@
 
 "@types/node@*", "@types/node@~12":
   version "12.6.6"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.6.6.tgz#831587377c35bb28fa33b6fe5f849a26a3f4a412"
+  resolved "https://registry.npmjs.org/@types/node/-/node-12.6.6.tgz#831587377c35bb28fa33b6fe5f849a26a3f4a412"
   integrity sha512-SMgj3x28MkJyHdWaMv/g/ca3LYDi5gR7O8mX0VKazvFOnmlDXctSEdd/8jfSqozjKFK1R9If1QZWkafX7yQTpA==
 
 "@types/normalize-package-data@^2.4.0":