chore: add CHANGELOG entry for url parameters feature

[circleci-app]

Summary

• Job 15680 failed because the shared RevenueCat Dangerfile requires CHANGELOG.md to be updated when source files are modified
• This PR adds an ## Unreleased section to CHANGELOG.md with an entry for the funnel URL parameters forwarding feature introduced in the parent branch

Test plan

• Danger check passes on CI after this CHANGELOG entry is present

https://app.circleci.com/agents/gh/RevenueCat/chat/6931eb3d-edfe-4d8f-a34a-9a99d029d483

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Note

Low Risk
Documentation-only change with no runtime or API impact.

Overview
Adds an Unreleased section to CHANGELOG.md so RevenueCat’s shared Danger check passes after source changes on the parent branch.

The new entry documents forwarding funnel URL parameters on checkout start—the SDK behavior that sends workflowPurchaseContext.urlParameters through postCheckoutStart (not implemented in this diff).

^{Reviewed by Cursor Bugbot for commit 50ecdad. Bugbot is set up for automated code reviews on this repo. Configure here.}

[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.

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