Docs: Convert all references to `main.*` and `preview.*` to links

[Sidnioulz]

To avoid people thinking a preview or main file must be TypeScript, we should always use .* as an extension and always link to the full docs, where we can be explicit about allowed extensions.

In inline snippets (e.g. ```ts title=".storybook/preview.tsx") and other places where we cannot or should not (e.g. headings) include a link, we should use ts or `tsx`, as appropriate.

Originally posted by @kylegach in #34396 (comment)