feat(core): add --config param to swizzle command

[e-im]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

My Docusaurus site uses a non-default config location and I am unable to use swizzle.

Test Plan

Because swizzle is not currently working out of the box on main, I've applied this additional diff for the sake of the test.

1. Move website/docusaurus.config.js to website/cfg.js.
2. Run yarn swizzle --config cfg.js.
3. See that swizzle works as intended.

Test links

N/A

Related issues/PRs

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[Josh-Cena]

Maybe add a test with a different config? (I forgot if we have similar tests)

[e-im]

I did not see that this was tested anywhere else, but I'll add tests in a few days.

[slorber]

yes we don't have test on other CLIs for now so that matches with our current practices 😅

LGTM thanks 👍