Refactor rollup configuration to use modern plugins and improve struc…

[vamshikiran065-jpg]

…ture

Overview

This PR updates the Rollup configuration to use maintained plugins and improves code readability.

Changes Made

• Replaced deprecated plugins with official Rollup plugins
• Simplified environment-based output logic
• Updated Babel configuration to modern standards
• Replaced uglify with terser for better minification
• Improved overall code structure and formatting

Why is this change needed?

These updates ensure better maintainability, compatibility with modern tooling, and improved build performance.

Overview

1. This PR fixes or fixes part of #[fill_in_number_here][(fill_in_the_issue_link)].
2. This PR does the following: [Explain here what your PR does and why]
3. (For bug-fixing PRs only) The original bug occurred because: [Explain what
   the cause of the bug was, and which PR introduced it]

Essential Checklist

• The PR title starts with "Fix #bugnum: " or "Fix part of #bugnum: ...", followed by a short, clear summary of the changes.
• I have followed the build process and "verifying your changes" section mentioned in the readme file.
• I have followed the instructions for making a code change.
• I have assigned the correct reviewers to this PR (or will leave a comment with the phrase "@{{reviewer_username}} PTAL" if I don't have permissions to assign reviewers directly).
• The linter/Karma presubmit checks pass on my local machine, and my PR follows the coding style guide).
• "Allow edits from maintainers" is checked. (See here for instructions on how to enable it.)

Proof that changes are correct

PR Pointers

• Never force push! If you do, your PR will be closed.
• To reply to reviewers, follow these instructions: https://github.com/oppia/oppia/wiki/Make-a-pull-request#step-5-address-review-comments-until-all-reviewers-approve
• Some e2e tests are flaky, and can fail for reasons unrelated to your PR. We are working on fixing this, but in the meantime, if you need to restart the tests, please check the "If your build fails" wiki page.
• See the Code Owner's wiki page for what code owners will expect.

[vamshikiran065-jpg]

Added the required change for this issue. Kindly review and let me know if any modifications are needed.
Thank you!