fix buffer import and use rollup for transpiling the package.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "nostr-tools",
-  "version": "0.6.2",
+  "version": "0.6.3",
   "description": "Tools for making a Nostr client.",
   "main": "dist/nostr-tools.esm.min.js",
   "module": "dist/nostr-tools.esm.min.js",
@@ -30,9 +30,6 @@
   "devDependencies": {
     "rollup": "^2.61.1"
   },
-  "files": [
-    "dist"
-  ],
   "scripts": {
     "prepublish": "rollup -c"
   }