fix: @jsii/check-node crashes on loading with older node releases

It was built with ES2020 target, which fails to load with Node 10 and 12 as
it makes use of the ?? syntax, which is not available in those releases.
Changing the TypeScript target so that code continues to load in older node
releases.

packages/@jsii/check-node/tsconfig.json

@@ -1,9 +1,14 @@
 {
   "extends": "../../../tsconfig-base",
   "compilerOptions": {
+    "target": "es2018", // Needs to target older releases of node or else it'll crash on start when using those
     "outDir": "./lib",
     "rootDir": "./src",
   },
-  "include": ["src/**/*.ts"],
-  "exclude": ["jest.config.ts"],
+  "include": [
+    "src/**/*.ts"
+  ],
+  "exclude": [
+    "jest.config.ts"
+  ],
 }