Add Timer (countdown) component

[SouravBandyopadhyay]

The @unlayer/exporters engine already shipped a first-class Timer (countdown) exporter, defaults, and types, but the React package never exposed a wrapper. Countdown timers are a core email-marketing element, so wire one through the existing component factory.

• Add Timer via createItemComponent (TimerExporters/TimerDefaults), exported from the barrel with TimerProps + TimerValues re-exported through shared.
• Expose an imageUrl prop (alias for countdown.countdownUrl) so authors can point at any server-rendered countdown image (NiftyImages, Sendtric, etc.). A countdown in email is a plain , not JS, so it is Gmail/Outlook-safe.
• Map alt -> altText and href -> action (storage shape) so links round-trip through renderToJson; pull width out to the display group to avoid the countdown.width name collision.
• Tests: Timer.test.tsx (no <script>, imageUrl verbatim, JSON round-trip), snapshot cases, and index export assertions. Add Timer stories and regenerate the Storybook visual-drift baseline.
• Commit the Storybook Node-global shims required for the exporter-backed stories to render in-browser (needed by the visual/smoke gates).

Test Plan

• pnpm build passes
• pnpm test passes
• Tested in Storybook (if UI change)
• Added/updated tests for new behavior

[ivoIturrieta]

Thanks for the contribution! @SouravBandyopadhyay would you mind checking the failing CI? you need to update the baseline for the storybook tests

[SouravBandyopadhyay]

fix(timer): resolve the baseline issue and updated json

• Closes Add <Timer> Component #24

[ivoIturrieta]

Thanks for the contribution! After discussing this further, we’re going to pause this PR while we revisit the timer API.

The Timer component should ideally work by accepting countdown props directly, without requiring users to generate or provide an imageUrl. Supporting that properly requires some backend work so we can securely generate and meter the countdown URL.

We’d prefer to settle that API contract before exposing the component publicly, rather than introduce an API we may need to change shortly afterward. We really appreciate the work you’ve put into this!