docs: Link initialization docs together

[waldyrious]

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

I came across an older project that still referenced the docusaurus-init package, which has been converted into create-docusaurus in #5635. I had a hard time figuring this out because the current docs don't make any mention of this, and the npm page for the old package doesn't indicate that it's been replaced either.

So I added links from the current initial setup docs to the page describing create-docusaurus, as well as a redirect from 'docusaurus-init' to 'create-docusaurus', so that people can still find the current page even when searching for the old name.

Test Plan

Test links

Direct links to affected pages:

• /docs/installation
• /docs/typescript-support
• /docs/api/misc/docusaurus-init

Related issues/PRs

[github-actions]

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/blog	🟠 63	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 48	🟢 92	🟢 100	🟢 100	Report
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[slorber]

thanks 👍