feat: Working on node builder

Sources/CliDoc/Nodes/Header.swift

@@ -0,0 +1,32 @@
+@preconcurrency import Rainbow
+
+public struct Header: NodeRepresentable {
+
+  @usableFromInline
+  let node: Text
+
+  @usableFromInline
+  let styles: [Style]
+
+  @inlinable
+  public init(
+    _ text: String,
+    color: NamedColor? = .yellow,
+    styles: [Style] = [.bold]
+  ) {
+    var text = Text(text)
+    if let color {
+      text = text.color(color)
+    }
+    self.node = text
+    self.styles = styles
+  }
+
+  @inlinable
+  public func render() -> String {
+    styles.reduce(node) { node, style in
+      node.style(style)
+    }
+    .render()
+  }
+}