feat: add init command (#1358)

[mdonnalley]

Merges #1358

Fixes #999

[mdonnalley]

@joshcanhelp FYI I've made a few changes. Feel free to push back on any of them

• added integration tests to ensure this works across package managers, operating systems, and module types
• made --output-dir a normal flag instead of a promptable flag. I think it'll be a better UX for oclif init to simply default to the current working directory without prompting
• removed the --module-type flag. I think it's safe to work off the type in the package.json and I can't imagine a reasonable scenario where someone with a CommonJS project would want to init oclif with the ESM bin scripts (or vice versa)
• added a --topic-separator promptable flag. I think it'll be nice for people to have that option set for them, especially since oclif defaults to colons - which few people actually want.
• run chmod on the bin scripts so that they're runnable
• install ts-node if it's not already there since it's needed for bin/dev.js
• a few code preference/quality changes

Again, feel free to push back on any of these changes

[joshcanhelp]

Everything makes sense to me except:

removed the --module-type flag. I think it's safe to work off the type in the package.json and I can't imagine a reasonable scenario where someone with a CommonJS project would want to init oclif with the ESM bin scripts (or vice versa)

My only hesitation here is that you can use .mjs and .cjs extensions to indicate the module type that you want to use without type being in the package.json (v18 docs and v20 docs and others going back).

[mdonnalley]

My only hesitation here is that you can use .mjs and .cjs extensions to indicate the module type that you want to use without type being in the package.json (v18 docs and v20 docs and others going back).

That's a good point that I hadn't considered. I'll add it back 👍