fix(wasm-utxo): set rootDir in tsconfig to fix output directory structure

TypeScript was preserving the js/ source directory in the output, creating
dist/esm/js/index.js instead of dist/esm/index.js. Setting rootDir: './js'
ensures the compiled files are placed directly in the output directory.

This fixes the module resolution error in wasm-utxo-ui where webpack couldn't
find '@bitgo/wasm-utxo' because the expected export paths didn't match the
actual file locations.

Author: OttoAllmendinger

packages/wasm-utxo/tsconfig.cjs.json

@@ -3,6 +3,7 @@
   "compilerOptions": {
     "module": "CommonJS",
     "moduleResolution": "node",
+    "rootDir": "./js",
     "outDir": "./dist/cjs"
   }
 }

packages/wasm-utxo/tsconfig.json

@@ -8,6 +8,7 @@
     "skipLibCheck": true,
     "declaration": true,
     "composite": true,
+    "rootDir": "./js",
     "outDir": "./dist/esm"
   },
   "include": ["./js/**/*.ts"],