Add Missing Methods for Layouts

[Cliftonz]

Some endpoints of the following section can't be hit from this SDK.

We would like to ensure that all endpoints can be hit. For this issue, we would like to build out the Layouts

Some of these methods may already exist. 
If so no need to change/update them, just point out that they already exist and we will close the issue.

This is just to bring every SDK we have on par with all the methods available.

Check all the endpoints here and add the missing ones.

[srikanth597]

None of the Layouts routes has been implemented in GO SDK, I would love to pick this & implement it.
Can you assign this to me?

[Cliftonz]

@srikanth597 Assigned

[srikanth597]

https://github.com/novuhq/go-novu/pull/65/files

@Cliftonz here's the Pull Request for the same

This is my first ever Open Source PR & also a first-ever GoLang Contribution outside personal learnings.

If you don't mind I need a favor, can you please add the Hactoberfest label to the Pull Request & to this issue that would be great for me to showcase that I have been part of the Hactoberfest 2023