Expand documentation on Multisig functionality for custom deploys

[devendran-m]

Problem Statement/Feedback (from Xord):

The documentation related to multisig functionality is also quite limited. While it briefly explains how to create and sign transfer deploys using multisignature, it doesn’t cover how to use multisignature for other deploys. For example, how can we create and sign custom deploys with multisignature beyond simple transfers? This area requires much more detailed guidance.

User Story:

As a developer working on the Casper Network,
I want detailed guidance on using multisignature functionality for custom deploys, beyond simple transfer deploys,
so that I can effectively implement and manage multisignature processes for a wider range of use cases.

Acceptance Criteria:

• The documentation includes a comprehensive section on multisignature functionality, covering both transfer and custom deploys.
• Step-by-step instructions are provided for creating and signing custom deploys using multisignature.
• Examples of common use cases for multisignature in custom deploys are included, with annotated code snippets.
• Limitations, best practices, and potential advantages of using multisignature functionality are outlined.
• Developers can successfully implement multisignature for custom deploys after referencing the documentation without additional support.
• Feedback from developers using multisignature functionality is incorporated to refine the documentation further.