docs: clarify description for redir directive

[felixauringer]

I find the current documentation for the redir directive slightly confusing.

It describes the HTTP status code 302 as temporary redirect. This is correct but the full status code is 302 Found and there is another status code 307 Temporary Redirect. In my opinion, those two can be easily confused with the current documentation.

Additionally, 308 Permanent Redirect is not mentioned although I would argue that it is often more appropriate than 301, for example for manual HTTP to HTTPS redirects.

I hope that my modifications improve the documentation in those regards.

[francislavoie]

Yeah we have some open discussions about this (see caddyserver/caddy#7348 and related issues) about possibly changing the default and possibly adding new named mappings to the status codes, but it hasn't gone anywhere yet.

[francislavoie]

Suggested change

	- `temporary` for a temporary redirect (`302 — Found`, this is the default)
	- `temporary` for a temporary redirect (`302 Found`, this is the default)

[francislavoie]

Suggested change

	- `permanent` for a permanent redirect (`301 — Moved Permanently`)
	- `permanent` for a permanent redirect (`301 Moved Permanently`)

[francislavoie]

Suggested change

	The status codes `307 — Temporary Redirect` and `308 — Permanent Redirect` should be used if the method must be the same in the second request.
	The status codes `307 Temporary Redirect` and `308 Permanent Redirect` should be used if the method must be the same in the second request.

[felixauringer]

Yeah we have some open discussions about this (see caddyserver/caddy#7348 and related issues) about possibly changing the default and possibly adding new named mappings to the status codes, but it hasn't gone anywhere yet.

I agree with Matt's opinion from the linked issue and do not want to changed the named status codes as that would probably break many existing setups.
However, I still think that the documentation could be a little bit more clear, hence this PR :)