accept registry option as LazyPath

This allows passing LazyPaths obtained from dependencies to
the vulkan-zig dependency, which streamlines using vulkan-zig
with Vulkan-Headers provided by the package manager.

README.md

@@ -50,14 +50,35 @@ There is also support for adding this project as a dependency through zig packag
 ```
 And then in your build.zig file, you'll need to add a line like this to your build function:
 ```zig
-const vkzig_dep = b.dependency("vulkan_zig", .{
-    .registry = @as([]const u8, b.pathFromRoot("path/to/vk.xml")),
-});
-const vkzig_bindings = vkzig_dep.module("vulkan-zig");
-exe.root_module.addImport("vulkan", vkzig_bindings);
+const vulkan = b.dependency("vulkan_zig", .{
+    .registry = b.path("path/to/vk.xml"),
+}).module("vulkan-zig");
+exe.root_module.addImport("vulkan", vulkan);
 ```
 That will allow you to `@import("vulkan")` in your executable's source.
 
+#### Generating bindings directly from Vulkan-Headers
+
+Bindings can be generated directly from the Vulkan-Headers repository by adding Vulkan-Headers as a dependency, and then passing the path to `vk.xml` from that dependency:
+```zig
+.{
+    // -- snip --
+    .dependencies = .{
+        // -- snip --
+        .vulkan_headers = .{
+            .url = "https://github.com/KhronosGroup/Vulkan-Headers/archive/v1.3.283.tar.gz",
+            .hash = "<dependency hash>",
+        },
+    },
+}
+```
+```zig
+const vulkan = b.dependency("vulkan_zig", .{
+    .registry = b.dependency("vulkan_headers", .{}).path("registry/vk.xml"),
+}).module("vulkan-zig");
+exe.root_module.addImport("vulkan", vulkan);
+```
+
 ### Manual generation with the package manager from build.zig
 
 Bindings can also be generated by invoking the generator directly. This may be useful is some special cases, for example, it integrates particularly well with fetching the registry via the package manager. This can be done by adding the Vulkan-Headers repository to your dependencies, and then passing the `vk.xml` inside it to vulkan-zig-generator: