[Playground] Fix bridge/payments documentation links (#8549)

https://linear.app/thirdweb/issue/PRO-148/fix-playground-doc-links-for-bridge-components

Update documentation links for bridge/payments widgets to follow consistent naming convention:
- Buy Widget: wallets/sponsor-gas → references/typescript/v5/BuyWidget
- Checkout Widget: payments → references/typescript/v5/CheckoutWidget
- Transaction Widget: wallets/sponsor-gas → references/typescript/v5/TransactionWidget
- Transaction Button: Add missing utm_source=playground parameter

All links now point to /references/typescript/v5/{WidgetName} with utm_source tracking.

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---

## PR-Codex overview
This PR updates the `docsLink` properties in several components to point to the correct documentation pages for various widgets in the `playground-web` application.

### Detailed summary
- Updated `docsLink` in `apps/playground-web/src/app/bridge/buy-widget/page.tsx` to point to `BuyWidget`.
- Updated `docsLink` in `apps/playground-web/src/app/bridge/checkout-widget/page.tsx` to point to `CheckoutWidget`.
- Updated `docsLink` in `apps/playground-web/src/app/bridge/transaction-button/page.tsx` to include `?utm_source=playground`.
- Updated `docsLink` in `apps/playground-web/src/app/bridge/transaction-widget/page.tsx` to point to `TransactionWidget`.

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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

* **Documentation**
  * Updated documentation links across playground widgets to reference current TypeScript v5 documentation resources.

<sub>✏️ Tip: You can customize this high-level summary in your review settings.</sub>

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: eabdelmoneim

apps/playground-web/src/app/bridge/buy-widget/page.tsx

@@ -26,7 +26,7 @@ export default function Page() {
         icon={ShoppingBagIcon}
         title={title}
         description={description}
-        docsLink="https://portal.thirdweb.com/wallets/sponsor-gas?utm_source=playground"
+        docsLink="https://portal.thirdweb.com/references/typescript/v5/BuyWidget?utm_source=playground"
       >
         <BuyPlayground />
       </PageLayout>

apps/playground-web/src/app/bridge/checkout-widget/page.tsx

@@ -26,7 +26,7 @@ export default function Page() {
         icon={CreditCardIcon}
         title={title}
         description={description}
-        docsLink="https://portal.thirdweb.com/payments?utm_source=playground"
+        docsLink="https://portal.thirdweb.com/references/typescript/v5/CheckoutWidget?utm_source=playground"
       >
         <CheckoutPlayground />
       </PageLayout>

apps/playground-web/src/app/bridge/transaction-button/page.tsx

@@ -25,7 +25,7 @@ export default function Page() {
         icon={ArrowLeftRightIcon}
         containerClassName="space-y-12"
         description={description}
-        docsLink="https://portal.thirdweb.com/references/typescript/v5/TransactionButton"
+        docsLink="https://portal.thirdweb.com/references/typescript/v5/TransactionButton?utm_source=playground"
         title={title}
       >
         <Example />

apps/playground-web/src/app/bridge/transaction-widget/page.tsx

@@ -26,7 +26,7 @@ export default function Page() {
         icon={ArrowLeftRightIcon}
         containerClassName="space-y-12"
         description={description}
-        docsLink="https://portal.thirdweb.com/wallets/sponsor-gas?utm_source=playground"
+        docsLink="https://portal.thirdweb.com/references/typescript/v5/TransactionWidget?utm_source=playground"
         title={title}
       >
         <TransactionPlayground />