added api call to get transak widget url

[andygruening]

Version Increment

Please ensure you have incremented the package version in the package.json as necessary.

• I have incremented the package.json according to semantic versioning
• No version increment is needed; the change does not impact SDK or Sample code/assets

Docs Checklist

Please ensure you have addressed documentation updates if needed as part of this PR:

• I have created a separate PR on the sequence docs repository for documentation updates: Link to docs PR
• No documentation update is needed for this change.