feat: import error for SIWXVerifier and other abstract classes

[Nithishvb]

Description

Closes: #3730

This PR fixes the import error for abstract classes in SIWX, specifically for SIWXVerifier, SIWXStorage, and SIWXMessenger. The classes are now correctly exported from the @reown/appkit-siwx package, allowing for successful imports in custom implementations.

Type of change

• Chore (non-breaking change that addresses non-functional tasks, maintenance, or code quality improvements)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Associated Issues

For Linear issues: Closes APKT-xxx
For GH issues: closes #...

Showcase (Optional)

Checklist

• Code in this PR is covered by automated tests (Unit tests, E2E tests)
• My changes generate no new warnings
• I have reviewed my own code
• I have filled out all required sections
• I have tested my changes on the preview link
• Approver of this PR confirms that the changes are tested on the preview link

[changeset-bot]

🦋 Changeset detected

Latest commit: ca18646

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@reown/appkit-siwx	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[vercel]

@Nithishvb is attempting to deploy a commit to the Reown Team on Vercel.

A member of the Team first needs to authorize it.