Be specific about zig version in readme (#996)

## What are the changes about?

There have been quite a few issues about the required zig version which
have appeared on codeberg recently. Largely these issues are opened
(like mine, #995) because individuals attempt to build using development
versions of zig and not the tagged releases.

The lack of a locked version (only a minimum) creates these issues.
Barring a locking mechanism, which I do not feel is my place to
implement, we should be clear to newer developers in Zig that you need
this specific version, not a development/master versioned release.

This is WIP mainly because I feel that a version file would be a better solution
than a README note, and I don't have enough zig experience or knowledge of
this repo to make a guess at what is best for this scenario.

## What existing issue does this resolve?

N/A

## Pre-requisites

- [x] I have tested & confirmed the changes work locally
- [x] I have run `zig fmt` throughout my changes

Co-authored-by: Louis Pate <louispate@gmail.com>
Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/996
Reviewed-by: AnErrupTion <anerruption+codeberg@disroot.org>

readme.md

@@ -14,7 +14,7 @@ Join us on Matrix over at [#ly-dm:matrix.org](https://matrix.to/#/#ly-dm:matrix.
 ## Dependencies
 
 - Compile-time:
-  - zig 0.16.x
+  - zig 0.16.x (you must use a __release version__ of zig; check that `zig version` does not have a `-dev*` suffix)
 
   - libc