asset: Add extrinsic documentation

[vidyaa01]

Comprehensive Documentation Update

This PR introduces comprehensive documentation for the following extrinsic functions in our pallet:

• create
• issue
• transfer
• status_change
• vc_create
• vc_issue
• vc_transfer
• vc_status_change

Each function now includes detailed Rustdoc comments covering:

• Purpose: What the function does.
• Parameters: Descriptions of input parameters.
• Return Values: Information on what the function returns.
• Potential Errors: Possible errors that can be encountered.
• Events Emitted: Events triggered by the function.

Fixes: #443

[vatsa287]

@vidyaa01 Run the cargo format for the ci test to pass.

cargo +nightly fmt --all

Add the changes again, amend the commit and push the changes.

[vidyaa01]

Hey @vatsa287 ,

I have made the changes you requested and pushed the changes to the PR. It shows me dismissed stale review which wasn't my intention, can you guide me on further steps?

[vatsa287]

@amarts PTAL

[VedantKhairnar]

Hello @vidyaa01 , Thanks for your contribution. As part of Augtoberfest, we want to reward you for your contributions, so pls fill out this form by 19th Sept. Thanks.