mach: implement key press/release callback

src/Engine.zig

@@ -2,6 +2,8 @@ const std = @import("std");
 const Allocator = std.mem.Allocator;
 const glfw = @import("glfw");
 const gpu = @import("gpu");
+const App = @import("app");
+const enums = @import("enums.zig");
 
 pub const VSyncMode = enum {
     /// Potential screen tearing.
@@ -68,6 +70,10 @@ timer: std.time.Timer,
 
 pub const Core = struct {
     internal: GetCoreInternalType(),
+
+    pub fn setKeyCallback(core: *Core, comptime cb: fn (app: *App, engine: *Engine, key: enums.Key, action: enums.Action) void) void {
+        core.internal.setKeyCallback(cb);
+    }
 };
 
 pub const GpuDriver = struct {