init: ignore `Cargo.*` and `contracts` in `frontend-template`

[chadoh]

While developing frontend templates, it's convenient to test them by adding the stuff that will come with the "backend" part of the contract init template, like contracts and Cargo.toml. Right now, in the new guide I created, I'm advising people not to commit these things, but we could reasonably expect people to do so anyhow, whether on purpose or not. It's just so useful!

I think we should probably just skip importing these files from the frontend template.

But be careful! We need to make sure we don't naïvely just skip importing any path that matches contracts, because it's common for frontend templates to include a src/contracts folder which should be copied over.

Further considerations

• I think we should probably just keep the frontend template's .gitignore, rather than merging the two. Frontend template authors will want to gitignore the .soroban & target folders, which is all the core .gitignore includes anyhow.
• Right now we skip importing the .github folder. I think we SHOULD include this one! I would like us to add a test to the official template which ensures that it actually works, and there's no reason to avoid adding this test to projects that use the template. In general, it seems like template consumers would want to end up with the .github folder that the original template had!

[ElliotFriend]

• Right now we skip importing the .github folder. I think we SHOULD include this one! I would like us to add a test to the official template which ensures that it actually works, and there's no reason to avoid adding this test to projects that use the template. In general, it seems like template consumers would want to end up with the .github folder that the original template had!

I agree! (fwiw)