feat: Working on node builder

Sources/CliDoc/Nodes/Group.swift

@@ -0,0 +1,38 @@
+
+public struct Group: NodeRepresentable {
+  @usableFromInline
+  let node: any NodeRepresentable
+
+  @usableFromInline
+  init(
+    separator: AnyNode,
+    node: any NodeRepresentable
+  ) {
+    if let many = node as? _ManyNode {
+      self.node = _ManyNode(many.nodes, separator: separator)
+    } else {
+      self.node = node
+    }
+  }
+
+  @inlinable
+  public init(
+    separator: any NodeRepresentable,
+    @NodeBuilder _ build: () -> any NodeRepresentable
+  ) {
+    self.init(separator: separator.eraseToAnyNode(), node: build())
+  }
+
+  @inlinable
+  public init(
+    separator: AnyNode = Space().eraseToAnyNode(),
+    @NodeBuilder _ build: () -> any NodeRepresentable
+  ) {
+    self.init(separator: separator, node: build())
+  }
+
+  @inlinable
+  public func render() -> String {
+    node.render()
+  }
+}