Docs: describe how to create multidimensional std::Array (#407)

doc: descirbe how to create multidimensional std::Array

Co-authored-by: paxcut <53811119+paxcut@users.noreply.github.com>

includes/std/array.pat

@@ -6,6 +6,22 @@ import std.core;
 /*!
     The array library contains a helper type to make it easier to create multi-dimensional arrays
     and pass arrays to functions as parameters.
+
+    ## Multi-dimensional arrays
+
+    The following example shows how to use multi-dimensional arrays with structs.
+
+    ```rust
+    import std.array;
+
+    struct File {
+        u8 width, height;
+        std::Array<std::Array<u8, parent.width>, height> cells;
+    };
+
+    File file @ 0x00;
+    ```
+
 */
 
 namespace auto std {