chore: output bundled files as dist/bundle.yaml (#88)

In the README, 'npm run build' bundles the definition to the dist folder.
However before the modification, the script outputed 'dist.yaml' in the root directory.
Therefore, 'dist.yaml' was marked as unmanaged by git.

Author: mahaker

package.json

@@ -7,7 +7,7 @@
   "private": true,
   "scripts": {
     "start": "redocly preview-docs",
-    "build": "redocly bundle -o dist",
+    "build": "redocly bundle -o dist/bundle.yaml",
     "test": "redocly lint"
   }
 }