feat: implement git submodules

[LetItRock]

What change does this PR introduce?

Implement Git Submodules for the private repository

Why was this change needed?

Other information (Screenshots)

[linear]

NV-2177 Implement Git Submodules for the private repository

Why? (Context)

We would like to have an ability to hide some parts of the code from the open-source. For ex. a code for the Timed Digest calculations stored in a private repository package. This package will be only available for the cloud and enterprise users.

What?

We are going to use Git Submodule pointing to the private repository: https://github.com/novuhq/packages-enterprise.git

Definition of Done

The private repository packages available as the Git submodule in the Novu main repository. Only the core dev team should have an access to it.

[scopsy]

Suggested change

	"packages-enterprise/*",
	"enterprise/*",

@LetItRock what do you think for jsut calling this enterprise as the folder?

[djabarovgeorge]

Hey there @LetItRock
I left a small question on the notion doc that is related to this PR
https://www.notion.so/Git-Submodules-243ac16a181c4bb49d51241c63bc9226?d=b8af0cbde51243dfbc1c8f4294ed1c5d#f1d48465df2a4ba1ac92bb7accf173b0

[LetItRock]

Hey there @LetItRock I left a small question on the notion doc that is related to this PR https://www.notion.so/Git-Submodules-243ac16a181c4bb49d51241c63bc9226?d=b8af0cbde51243dfbc1c8f4294ed1c5d#f1d48465df2a4ba1ac92bb7accf173b0

@djabarovgeorge thanks for the suggestion, I've added it the way you suggested ;)