### What
Skip writing files from the template if the files already exist in the
project directory.
### Why
When I run deno init in a directory that already has a main.ts, or one
of the other template files, I usually want to initialize a workspace
around a file I've started working in. A hard error in this case seems
counter productive. An informational message about what's being skipped
seems sufficient.
Close #20433
4a8b873111