feat: Moves core functionality into it's own library.

Sources/CliDocCore/Nodes/VStack.swift

@@ -0,0 +1,23 @@
+public struct VStack: TextNode {
+
+  @usableFromInline
+  let content: [any TextNode]
+
+  @usableFromInline
+  let separator: any TextNode
+
+  @inlinable
+  public init(
+    spacing: Int = 1,
+    @TextBuilder content: () -> any TextNode
+  ) {
+    self.content = array(from: content())
+    self.separator = seperator("\n", count: spacing > 0 ? spacing - 1 : 0)
+  }
+
+  @inlinable
+  public var body: some TextNode {
+    content.removingEmptys()
+      .joined(separator: separator.render())
+  }
+}