feat: Working on node builder

Sources/CliDoc/Nodes/AnyNode.swift

@@ -0,0 +1,27 @@
+public struct AnyNode: NodeRepresentable {
+  @usableFromInline
+  let node: any NodeRepresentable
+
+  @inlinable
+  public init<N: NodeRepresentable>(@NodeBuilder _ build: () -> N) {
+    self.node = build()
+  }
+
+  @inlinable
+  public init<N: NodeRepresentable>(_ node: N) {
+    self.node = node
+  }
+
+  @inlinable
+  public func render() -> String {
+    node.render()
+  }
+}
+
+public extension NodeRepresentable {
+
+  @inlinable
+  func eraseToAnyNode() -> AnyNode {
+    .init(self)
+  }
+}