improve build setup

local/rollup/src/plugins/clean.js

@@ -5,7 +5,7 @@ module.exports = ({ paths = [], verbose = false } = {}) => {
   let cleaned = false;
   return {
     name: 'clean',
-    async buildStart() {
+    buildStart() {
       if (!cleaned) {
         paths.forEach((currPath) => {
           const resolvedPath = path.resolve(currPath);

local/rollup/src/plugins/copy.js

@@ -0,0 +1,25 @@
+const path = require('path');
+const fs = require('fs');
+
+module.exports = ({ paths = [], verbose = false } = {}) => {
+  return {
+    name: 'copy',
+    buildStart() {
+      paths.forEach((currPath) => {
+        const resolvedPath = path.resolve(currPath);
+
+        if (fs.existsSync(resolvedPath)) {
+          if (verbose) {
+            // eslint-disable-next-line no-console
+            console.log(`Copy: ${resolvedPath}`);
+          }
+          this.emitFile({
+            type: 'asset',
+            source: fs.readFileSync(resolvedPath),
+            fileName: path.basename(resolvedPath),
+          });
+        }
+      });
+    },
+  };
+};

local/rollup/src/plugins/packageJson.js

@@ -0,0 +1,20 @@
+const path = require('path');
+
+module.exports = ({ input = 'package.json', output = 'package.json', json } = {}) => {
+  const resolvedInput = path.resolve(input);
+  const inputPackageJson = require(resolvedInput);
+  return {
+    name: 'packageJson',
+    buildStart() {
+      this.emitFile({
+        type: 'asset',
+        source: JSON.stringify(
+          typeof json === 'function' ? json(inputPackageJson) : inputPackageJson,
+          null,
+          2
+        ),
+        fileName: output,
+      });
+    },
+  };
+};