Convert punctuateSeries to TypeScript

[vtejasri1511-sudo]

Fixes #3533

Changes proposed in this pull request:

• Converted framework/core/js/src/common/helpers/punctuateSeries from JavaScript to TypeScript.
• No behavior or API changes intended; this is a small isolated step in the ongoing core JS → TS migration.

Reviewers should focus on:

• Confirm logic is unchanged (only typing / file extension change).
• Confirm TS types (mithril Children) are appropriate and build tooling accepts the new .ts file.

Screenshot
N/A (no user-facing change)