Ignore .git directory when checking if outDir is empty

[lukecarr]

(Semi-related to #582, but not a duplicate)

It would be really handy if the .git directory is ignored when [out-dir] is checked for existing contents. Adding --overwrite-dir in v3.7.0 was a step in the right direction, but I (and I believe many others) would still prefer the safety of not using a forceful operation when running the cli in a cloned empty repository (with a .git directory).

A common workflow for many is:

• Clone empty repository.
• Run create-nuxt-app without providing an outDir.
• Get an error because the directory technically isn't empty (.git).
• Re-run create-nuxt-app providing an outDir.
• Immediately copy all of the generated files out of the outDir into the root of the repository.
• Delete the leftover outDir.

This is obviously a fairly opinionated issue, but I'd love to hear some counter arguments.