feat: allow the same namespace but different files

[imnotjames]

Closes #69

this allows you to install multiple templates under the same
namepace

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[imnotjames]

Need to add tests..

[imnotjames]

A few comments:

The templating/filesystem tests were completely missing so I added some.

I moved mkdir to utils/fs out of templating/filesystem to simplify testing.

I removed a definition of debug and an export of fileExists - neither of which were in use.

There seems to be a few bugs that I found during writing tests. I'll make sure to open issues & eventual PRs to fix them. However, for now I've gone ahead and "documented" the bugs with tests that verify the behavior.

I pulled in listr-silent-renderer explicitly instead of transitively so listr output can be disabled for tests.

I experimented with mock-fs for testing these filesystem changes and it interacted poorly with some dynamic module loading being done.

[dkundel]

Hey @imnotjames! Sorry for the late review and thank you so much for your contribution. I'll try to get back to this as soon as possible to take a look at it. Thank you!

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