fix(tsconfig): set explicit rootDir to silence TS6059 in consumer IDEs (#211)

The shipped tsconfig.json sets outDir without rootDir, which causes
TypeScript >=5.x to emit a TS6059 hint in consumer IDEs that validate
the vendor config. Setting rootDir to ./src matches what TypeScript
already infers and follows the team's recommended migration.
Closes #209

Author: mandarini

tsconfig.json

@@ -12,6 +12,7 @@
     "noImplicitOverride": true,
     "module": "preserve",
     "outDir": "dist/module",
+    "rootDir": "./src",
     "sourceMap": true,
     /* AND if you're building for a library: */
     "declaration": true,