docs: fix pull request template path and expand checklist

[BittuBarnwal7479]

Summary

The PR template was in the wrong location:

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

Because of this, GitHub did not apply it automatically. Moving it to .github/pull_request_template.md makes it the default PR template.

While fixing the location, I also updated the template to:

• Add a Linked issue section.
• Add a Screenshots section for visual changes.
• Add the required conventional commit title and signed commits checks.
• Add links to the Code of Conduct and Contributing guidelines.

Verification

• npm run format:check passes.
• Checked for references to the old template path; none found.
• Verified all added links return HTTP 200.
• Confirmed the template renders correctly without empty screenshot tables.
• No source, test, or build files were changed.

Notes for Reviewers

• Git shows the change as a delete + add because the content changed beyond the rename threshold.
• Used docs: because this is a documentation/template-only change and should not trigger a release.
• The automatic template behavior can only be verified after this PR is merged.

Checklist

• PR title follows [conventional commit style](https://www.conventionalcommits.org/en/v1.0.0/#summary)
• Commits are signed
• Documentation updated if needed
• Tests added or updated if behavior changed
• npm run check passes
• I have read the [Code of Conduct](https://github.com/reponomics/PolicyChecks/blob/main/CODE_OF_CONDUCT.md) and [Contributing guidelines](https://github.com/reponomics/PolicyChecks/blob/main/CONTRIBUTING.md)