tools: enable type checking within the internal/modules directory

Author: JakobJingleheimer

lib/internal/modules/tsconfig.json

@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "allowJs": true,
+    "checkJs": true,
+    "declaration": true,
+    "emitDeclarationOnly": true,
+  },
+  "include": [
+    "./",
+    "../../../typings",
+  ]
+}