docs: update resources API docs

docs/api/resources/texture/getusage.md

@@ -0,0 +1,29 @@
+# Texture::GetUsage
+
+```cpp
+TextureUsage GetUsage() const
+```
+
+获取纹理用途标志。用途标志可组合使用。
+
+**参数：** 无
+
+**返回：** `TextureUsage` 枚举值
+
+**线程安全：** ✅
+
+**示例：**
+
+```cpp
+Texture tex;
+tex.Create(1024, 1024, 1, 1, 
+    TextureType::Texture2D, 
+    TextureFormat::RGBA8_UNORM, 
+    nullptr, 0);
+TextureUsage usage = tex.GetUsage(); // 返回 TextureUsage::ShaderResource
+```
+
+## 相关文档
+
+- [Texture 总览](texture.md) - 返回类总览
+- [TextureUsage 枚举](./texture.md#textureusage) - 用途枚举说明