Add Missing Methods for Feeds

[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 Feeds Feature

Get Feeds - https://docs.novu.co/api-reference/feeds/get-feeds
Create Feed - https://docs.novu.co/api-reference/feeds/create-feed
Delete Feed - https://docs.novu.co/api-reference/feeds/delete-feed

[ShatilKhan]

I'd like to work on this issue. Please assign it to me.
I already made some contributions to novu docs today

[unicodeveloper]

@ShatilKhan Please have you worked with Elixir before?

[ShatilKhan]

I'll get to work on this.Thanks!