Support Editing of Media Message Captions in Message Composer

Introduce native support in the UI Kit and SDK for editing captions of media messages (such as images, videos, audio, and documents) directly within the message composer. Currently, while developers can implement captions for media using custom CometChatMessageTemplate, there is no built-in mechanism to edit these captions once the message is sent. This limitation forces developers to create complex custom workflows, which do not integrate seamlessly with the existing composer or editing flow. Providing a standardized solution—where media captions can be edited similar to text messages within the composer—would ensure consistency, reduce implementation overhead, and significantly improve both developer experience and end-user usability.