warn when initializing/overwriting non-empty directory

[scarf005]

Enter your suggestions in details:

when running deno run -A https://lume.land/init.ts it will edit

File saved: deno.json
File saved: _config.ts
File saved: .gitignore
File saved: _cms.ts

without checking whether these files exist.
could be problemetic if user(me) accidently initialized it on wrong path, potentially wiping important stuff like .gitignore

[oscarotero]

The init script is in a different repository
but yeah, probably there should be a confirm before overriding existing files.