Update MenuItemsBuilder to support optional and either blocks

Author: stackotter

Sources/SwiftCrossUI/Builders/MenuItemsBuilder.swift

@@ -13,6 +13,10 @@ public struct MenuItemsBuilder {
         [.submenu(first)]
     }
 
+    public static func buildPartialBlock(first: Block) -> [MenuItem] {
+        first.items
+    }
+
     public static func buildPartialBlock(
         accumulated: [MenuItem],
         next: Button
@@ -33,4 +37,29 @@ public struct MenuItemsBuilder {
     ) -> [MenuItem] {
         accumulated + [.submenu(next)]
     }
+
+    public static func buildPartialBlock(
+        accumulated: [MenuItem],
+        next: Block
+    ) -> [MenuItem] {
+        accumulated + next.items
+    }
+
+    public static func buildOptional(_ component: [MenuItem]?) -> Block {
+        Block(items: component ?? [])
+    }
+
+    public static func buildEither(first component: [MenuItem]) -> Block {
+        Block(items: component)
+    }
+
+    public static func buildEither(second component: [MenuItem]) -> Block {
+        Block(items: component)
+    }
+
+    /// An implementation detail of ``MenuItemBuilder``'s support for
+    /// `if`/`else if`/`else` blocks.
+    public struct Block {
+        var items: [MenuItem]
+    }
 }