Feature: Add custom command & label support (#945)

## What are the changes about?

Adds customizable commands and labels to ly.
Solves https://codeberg.org/fairyglade/ly/issues/905.

Since Ly doesn't use INI headers. I use them exclusively for declarations of custom commands and labels.

### Commands

Bind a keybind to a command, and add a hint to the HUD. Useful for use cases like display brightness, switching between GPUs, etc.

Supports localization in the `name` field only. ex: where `lang = es`: `$brightness_up` => `bajar brillo`

Declared in config.ini with the following:

```ini
[cmd:F8]
name = custom command 2
cmd = touch /tmp/ly.gaming
```

### Labels

Add a label to the HUD. As specified in #905.
The text of the label corresponds to the output of the command specified in `[lbl:NAME]`.
Only shows the first line of the output.

Declared in config.ini with the following:

```ini
[lbl:kernel]
cmd = uname -srn
refresh = 0
```

Example to add to the config.ini:
```ini
# Declare a command with the F8 binding.
[cmd:F8]
#The name of the command to show up in Ly.
name = custom command
cmd = touch /tmp/ly.gaming

# Declare a label with an ID. This ID should be unique across all labels.
[lbl:kernel]
cmd = uname -srn
# In frames, the time to re-run the command and update the label. If 0, only run once- do not refresh.
refresh = 0

# Once you're done setting up labels and commands, add an empty header
# below to continue configurating the rest of Ly.
# Put other settings not belonging to custom commands/labels below here.
[]

```

## Pre-requisites

- [x] I have tested & confirmed the changes work locally

![image](/attachments/f9373ac9-567e-4f47-987c-1df6f4ee0d84)

Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/945
Reviewed-by: AnErrupTion <anerruption+codeberg@disroot.org>
Co-authored-by: RadsammyT <radsammyt@gmail.com>
Co-committed-by: RadsammyT <radsammyt@gmail.com>

src/config/migrator.zig

@@ -16,6 +16,7 @@ const ini = ly_core.ini;
 const Config = @import("Config.zig");
 const OldSave = @import("OldSave.zig");
 const SavedUsers = @import("SavedUsers.zig");
+const custom = @import("custom.zig");
 
 const color_properties = [_][]const u8{
     "bg",
@@ -162,6 +163,61 @@ pub fn configFieldHandler(_: std.mem.Allocator, field: ini.IniField) ?ini.IniFie
         return mapped_field;
     }
 
+    // TODO: Dearest Melpert,
+    //      I pray this message finds you well, as daylight dwindles and the witching hour
+    //      approaches, I find it more and more imperative as time continues that I place
+    //      this reminder here in such a format that you cannot ignore.
+    //      Do you know how long I have been waiting for this petition to be authorized
+    //      in regards to this particular segment of computerized instructions?
+    //      It has been many a moon since this particular audit has been
+    //      posted regarding the position of handling configurable literature 
+    //      apparatuses and plans for a new feature to the configuration
+    //      interface and as time continues onwards I grow more restless
+    //      on the progress of said interface, only to find out afterwards
+    //      that you have PROCRASTINATED on the efforts meant to enhance
+    //      configuration. Thus the requirement for this reminder larger
+    //      compared to the two reminders regarding better methods of
+    //      X termination detection and new usernames with existing 
+    //      save files.
+    //
+    //      Thus is my que to leave this TODO at thy request,
+    //      
+    //      Forever Sullied,
+    //
+    //      Ly Contributor.
+    //
+    if (std.mem.startsWith(u8, field.header, "cmd:")) {
+        const key = field.header["cmd:".len..];
+        const keyZ = temporary_allocator.dupe(u8, key) catch "";
+        if (!custom.binds.contains(key)) {
+            custom.binds.put(keyZ, .{}) catch {};
+        }
+        if (custom.binds.getPtr(keyZ)) |command| {
+            if (std.mem.eql(u8, field.key, "name")) {
+                command.name = temporary_allocator.dupe(u8, field.value) catch "";
+            }
+            if (std.mem.eql(u8, field.key, "cmd")) {
+                command.cmd = temporary_allocator.dupe(u8, field.value) catch "";
+            }
+        }
+    }
+
+    if (std.mem.startsWith(u8, field.header, "lbl:")) {
+        const key = field.header["lbl:".len..];
+        const keyZ = temporary_allocator.dupe(u8, key) catch "";
+        if (!custom.labels.contains(keyZ)) {
+            custom.labels.put(keyZ, .{ .name = keyZ }) catch {};
+        }
+        if (custom.labels.getPtr(keyZ)) |label| {
+            if (std.mem.eql(u8, field.key, "cmd")) {
+                label.cmd = temporary_allocator.dupe(u8, field.value) catch "";
+            }
+            if (std.mem.eql(u8, field.key, "refresh")) {
+                label.refresh = std.fmt.parseInt(u32, field.value, 10) catch 0;
+            }
+        }
+    }
+
     return field;
 }