Add docs for the DELIFEQ command

[LinusU]

(note that I did use ChatGPT 4o to help me with parts of this PR, but I've verified the accuracy of everything)

This adds documentation for the DELIFEQ command that I added in valkey-io/valkey#1975

[zuiderkwast]

Looks perfect!

Can you also update the page about locking to use DELIFEQ instead of EVAL? https://github.com/valkey-io/valkey-doc/blob/main/topics/distlock.md

We should mention DELIFEQ first, and below we can mention with less focus that before 9.0, you'd have to use the Lua script.

[LinusU]

@zuiderkwast done ✅

[zuiderkwast]

Thanks Linus! Looks perfect. I was going to merge it, but I just realized the replies are documented in https://github.com/valkey-io/valkey-doc/blob/main/resp2_replies.json and https://github.com/valkey-io/valkey-doc/blob/main/resp3_replies.json and taken from there when the pages are rendered. Can you add the reply info to these too?

(I opened #312 to get rid of this weird setup that we have for unknown historical reasons.)

[LinusU]

@zuiderkwast fixed ✅