xcb: add Vulkan init to sample

packages/xcb/sample/root.zig

@@ -1,9 +1,15 @@
 const std = @import("std");
 const xcb = @import("xcb");
 
-pub fn main(init: std.process.Init) !void {
-    _ = init;
+const Vulkan = @import("Vulkan.zig");
 
+// Declarations picked up by "vulkan" module
+
+pub const xcb_connection_t = xcb.Connection;
+pub const xcb_visualid_t = xcb.Visualid;
+pub const xcb_window_t = xcb.Window;
+
+pub fn main(init: std.process.Init) !void {
     const connection = xcb.Connection.connect(null, null);
     defer connection.disconnect();
 
@@ -64,6 +70,9 @@ pub fn main(init: std.process.Init) !void {
     _ = connection.mapWindow(window);
     _ = connection.flush();
 
+    var vulkan = try Vulkan.init(init.gpa, connection, window);
+    defer vulkan.deinit(init.gpa);
+
     var running = true;
     while (running) {
         if (connection.waitForEvent()) |event| {