Add item elements URL generation

[petrsvihlik]

Kentico Kontent provides a way of accessing specific content items in Kentico Kontent UI via URL.
Here is information, how to do that:

• https://docs.kontent.ai/tutorials/write-and-collaborate/preview-content/editing-content-directly-from-your-app

Blog post showcasing them:

• https://kontent.ai/blog/edit-your-content-directly-from-website

Similarly to kontent-ai/management-sdk-net#9, add functionality for generating content item URLs to the KK Management SDK.

Result:

• probably a separate package, similarly to Kentico.Kontent.Management.Helpers + NuGet

Blocks:

• Add Preview Edit Links sample-app-vue#4
• Add Preview Edit Links sample-app-react#81