feat: adding item templates from old template package

[Mantus667]

Integrating item templates from the v8 template package

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes

Description

For v8 we had item templates provided by the Packages.Templates templates pack.
These templates were provided by the Package Team. As with v9 Umbraco HQ provides general Dotnet templates for project/package, the team decided that we should move the item templates to the offical umbraco repo and be part of the official templates pack.

How to test:

• Pack the templates locally
• Install the templates from the local nuget package
• Use the item templates to install them into an exisitng umbraco project

[github-actions]

Hi there @Mantus667, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• 💡 The contribution looks original and the contributor is presumably allowed to share it

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[nul800sebastiaan]

@Mantus667 I think this relates to #12869 as well. Can you let us know if this is still relevant and correct? Or maybe there's new ideas at the moment?

[ronaldbarendse]

@Mantus667 I think this relates to #12869 as well. Can you let us know if this is still relevant and correct? Or maybe there's new ideas at the moment?

Making it easier and faster to create packages/extensions will always be relevant, but we might want to verify whether the effort is indeed justified 😄

The first one to check will be how these item templates are exposed: can you only use the dotnet new CLI command (docs) or will these also be exposed in the IDE (e.g. similar to adding items to the Add New Item dialog in Visual Studio, as that can be done in another way)?

We should probably also use a similar structure as the UI Examples, where each created item has its own package.manifest file, as I don't think the item templates can update an existing package.manifest file, add translation keys to the XML files, etc.

And finally we should also look into how this will work in v13, as that will definitely change how things need to be done and potentially move this part to npm packages instead of using .NET 🤷🏻

[nul800sebastiaan]

Hey there @Mantus667! It's been a while since we've heard from you. We'd love to keep going on this one but it seems like it doesn't fit in for you at the moment. In order to keep things tidy, we'll close this one for now. Please let us know when you can get back to it, we can either resurrect this PR or go for an attempt number 2! Thanks again for all your work on this and we hope to hear from you soon! 🙌