chore: Introduce unjs/unbuild

.eslintrc

@@ -12,7 +12,8 @@
     "plugin:prettier/recommended"
   ],
   "ignorePatterns": [
-    "tsup.config.ts"
+    "tsup.config.ts",
+    "build.config.ts"
   ],
   "globals": {
     "Atomics": "readonly",

build.config.ts

@@ -0,0 +1,46 @@
+import { defineBuildConfig } from 'unbuild';
+import { name, version } from './package.json';
+
+// https://github.com/unjs/unbuild
+export default defineBuildConfig({
+  declaration: true,
+  failOnWarn: false,
+  rollup: {
+    esbuild: {
+      minify: false,
+    },
+  },
+  entries: [
+    // mkdist builder transpiles file-to-file keeping original sources structure
+    {
+      builder: 'mkdist',
+      input: './src/',
+      outDir: './dist',
+      format: 'esm',
+      pattern: ['**', '!**/*.test.ts'],
+      esbuild: {
+        define: {
+          PACKAGE_VERSION: `"${version}"`,
+          PACKAGE_NAME: `"${name}"`,
+        },
+      },
+    },
+    {
+      builder: 'mkdist',
+      input: './src/',
+      outDir: './dist',
+      format: 'cjs',
+      ext: 'cjs',
+      // https://github.com/sindresorhus/globby
+      pattern: ['**', '!**/*.test.ts'],
+      // Declarations already created for esm build
+      declaration: false,
+      esbuild: {
+        define: {
+          PACKAGE_VERSION: `"${version}"`,
+          PACKAGE_NAME: `"${name}"`,
+        },
+      },
+    },
+  ],
+});