Use Lua as a config file language (#1010)

## What are the changes about?

Adds zlua for running Lua code as the configuration file.
Missing as of this time:
- ~~Parsing custom binds and labels~~
- ~~Fix memory leaks~~
- ~~Investigate issue with animation colours~~
- ~~Add examples and default config~~

## What existing issue does this resolve?

[#976](https://codeberg.org/fairyglade/ly/issues/976)

## Pre-requisites

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

Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/1010
Reviewed-by: AnErrupTion <anerruption+codeberg@disroot.org>

ly-core/build.zig

@@ -21,6 +21,13 @@ pub fn build(b: *std.Build) void {
     const zigini = b.dependency("zigini", .{ .target = target, .optimize = optimize });
     mod.addImport("zigini", zigini.module("zigini"));
 
+    const zlua = b.dependency("zlua", .{
+        .target = target,
+        .optimize = optimize,
+        .lang = .luajit,
+    });
+    mod.addImport("zlua", zlua.module("zlua"));
+
     const translate_c = b.dependency("translate_c", .{
         .target = target,
     });