async execution (#53)

<!-- This is an auto-generated comment: release notes by openai -->
### Summary by OpenAI

**Release Notes**

This pull request includes two changes to improve the functionality and
efficiency of the software.

- New Feature: Added `clone()` method to clone Inputs object in
`src/options.ts`.
- Refactor: Retrieve file contents and diff for review, and filter out
null results. Use Promise.all to run file review processes in parallel
in `src/review.ts`.

These changes should enhance the user experience by improving the
performance of the software.
<!-- end of auto-generated comment: release notes by openai -->

Author: harjotgill

dist/index.js

@@ -134,6 +134,22 @@ export class Inputs {
     this.comment = comment
   }
 
+  clone(): Inputs {
+    return new Inputs(
+      this.system_message,
+      this.title,
+      this.description,
+      this.summary,
+      this.filename,
+      this.file_content,
+      this.file_diff,
+      this.patch,
+      this.diff,
+      this.comment_chain,
+      this.comment
+    )
+  }
+
   render(content: string): string {
     if (!content) {
       return ''