feat(utxo-core): add ESM build support

Update package.json and add ESM-specific tsconfig to support both CJS and
ESM module formats. Adjust output paths and package exports accordingly.

Issue: BTC-2732

Co-authored-by: llm-git <llm-git@ttll.de>

Author: OttoAllmendinger

modules/utxo-core/package.json

@@ -2,25 +2,60 @@
   "name": "@bitgo/utxo-core",
   "version": "1.23.0",
   "description": "BitGo UTXO Core types",
-  "main": "./dist/src/index.js",
-  "types": "./dist/src/index.d.ts",
+  "main": "./dist/cjs/src/index.js",
+  "module": "./dist/esm/index.js",
+  "browser": "./dist/esm/index.js",
+  "types": "./dist/cjs/src/index.d.ts",
   "files": [
-    "dist/src"
+    "dist/cjs",
+    "dist/esm"
   ],
   "exports": {
-    ".": "./dist/src/index.js",
-    "./descriptor": "./dist/src/descriptor/index.js",
-    "./testutil": "./dist/src/testutil/index.js",
-    "./testutil/descriptor": "./dist/src/testutil/descriptor/index.js"
-  },
-  "browser": {
-    ".": "./dist/src/index.js",
-    "./descriptor": "./dist/src/descriptor/index.js",
-    "./testutil": "./dist/src/testutil/index.js",
-    "./testutil/descriptor": "./dist/src/testutil/descriptor/index.js"
+    ".": {
+      "import": {
+        "types": "./dist/esm/index.d.ts",
+        "default": "./dist/esm/index.js"
+      },
+      "require": {
+        "types": "./dist/cjs/src/index.d.ts",
+        "default": "./dist/cjs/src/index.js"
+      }
+    },
+    "./descriptor": {
+      "import": {
+        "types": "./dist/esm/descriptor/index.d.ts",
+        "default": "./dist/esm/descriptor/index.js"
+      },
+      "require": {
+        "types": "./dist/cjs/src/descriptor/index.d.ts",
+        "default": "./dist/cjs/src/descriptor/index.js"
+      }
+    },
+    "./testutil": {
+      "import": {
+        "types": "./dist/esm/testutil/index.d.ts",
+        "default": "./dist/esm/testutil/index.js"
+      },
+      "require": {
+        "types": "./dist/cjs/src/testutil/index.d.ts",
+        "default": "./dist/cjs/src/testutil/index.js"
+      }
+    },
+    "./testutil/descriptor": {
+      "import": {
+        "types": "./dist/esm/testutil/descriptor/index.d.ts",
+        "default": "./dist/esm/testutil/descriptor/index.js"
+      },
+      "require": {
+        "types": "./dist/cjs/src/testutil/descriptor/index.d.ts",
+        "default": "./dist/cjs/src/testutil/descriptor/index.js"
+      }
+    }
   },
   "scripts": {
-    "build": "yarn tsc --build --incremental --verbose .",
+    "build": "npm run build:cjs && npm run build:esm",
+    "build:cjs": "yarn tsc --build --incremental --verbose .",
+    "build:esm": "yarn tsc --project tsconfig.esm.json",
     "fmt": "prettier --write .",
     "check-fmt": "prettier --check '**/*.{ts,js,json}'",
     "clean": "rm -r ./dist",
@@ -45,7 +80,6 @@
   "publishConfig": {
     "access": "public"
   },
-  "type": "commonjs",
   "nyc": {
     "extension": [
       ".ts"

modules/utxo-core/tsconfig.esm.json

@@ -0,0 +1,18 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "./dist/esm",
+    "rootDir": "./src",
+    "module": "ES2020",
+    "target": "ES2020",
+    "moduleResolution": "bundler",
+    "lib": ["ES2020", "DOM"],
+    "declaration": true,
+    "declarationMap": true,
+    "skipLibCheck": true
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "test", "dist"],
+  "references": []
+}
+

modules/utxo-core/tsconfig.json

@@ -1,11 +1,13 @@
 {
   "extends": "../../tsconfig.json",
   "compilerOptions": {
-    "outDir": "./dist",
+    "outDir": "./dist/cjs",
     "rootDir": "./",
     "esModuleInterop": true,
     "allowJs": false,
-    "strict": true
+    "strict": true,
+    "moduleResolution": "node16",
+    "module": "node16"
   },
   "include": ["src/**/*", "test/**/*"],
   "exclude": ["node_modules"],