Add webCheckoutUrl to API testers

[tonidero]

Summary

• Adds webCheckoutUrl type checks to API testers for PurchasesPackage and PurchasesOffering
• Types flow from @revenuecat/purchases-typescript-internal

Depends on: purchases-hybrid-common release with webCheckoutUrl types

Test plan

• Compile API testers (tsc)

🤖 Generated with Claude Code

[RevenueCat-Danger-Bot]

	1 Error
🚫	Label the PR using one of the change type labels. If you are not sure which label to use, choose pr:other.

Label	Description
pr:feat	A new feature. Use along with pr:breaking to force a major release.
pr:fix	A bug fix. Use along with pr:force_minor to force a minor release.
pr:other	Other changes. Catch-all for anything that doesn't fit the above categories. Releases that only contain this label will not be released. Use along with pr:force_patch, or pr:force_minor to force a patch or minor release.
pr:RevenueCatUI	Use along any other tag to mark a PR that only contains RevenueCatUI changes
pr:next_release	Preparing a new release
pr:dependencies	Updating a dependency
pr:phc_dependencies	Updating purchases-hybrid-common dependency
pr:changelog_ignore	The PR will not be included in the changelog. This label doesn't determine the type of bump of the version and must be combined with pr:feat, pr:fix or pr:other.

Generated by 🚫 Danger