Improve tsconfig.json

* Use moduleResolution: bundler to enable conditional imports and exports
* Add "fastly" custom condition to match js-compute-runtime
* Remove skipLibCheck as that is no longer needed

tsconfig.json

@@ -3,12 +3,12 @@
     "strict": true,
     "module": "ES2022",
     "target": "ES2022",
-    "moduleResolution": "node",
+    "moduleResolution": "bundler",
+    "customConditions": [ "fastly" ],
     "esModuleInterop": true,
-    "lib": [ "es2022" ],
+    "lib": [ "ES2022" ],
     "rootDir": "src",
-    "outDir": "build",
-    "skipLibCheck": true
+    "outDir": "build"
   },
   "include": [
     "./src/**/*.js",