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

Sources/CliDocCore/Modifiers/ColorModifier.swift

@@ -0,0 +1,24 @@
+import Rainbow
+
+public extension TextNode {
+  @inlinable
+  func color(_ color: NamedColor) -> some TextNode {
+    modifier(ColorModifier(color: color))
+  }
+}
+
+@usableFromInline
+struct ColorModifier<Content: TextNode>: NodeModifier {
+  @usableFromInline
+  let color: NamedColor
+
+  @usableFromInline
+  init(color: NamedColor) {
+    self.color = color
+  }
+
+  @usableFromInline
+  func render(content: Content) -> some TextNode {
+    content.render().applyingColor(color)
+  }
+}

Sources/CliDocCore/Modifiers/TextStyleModifier.swift

@@ -0,0 +1,32 @@
+import Rainbow
+
+public extension TextNode {
+  @inlinable
+  func textStyle(_ styles: Style...) -> some TextNode {
+    modifier(StyleModifier(styles: styles))
+  }
+
+  @inlinable
+  func textStyle(_ styles: [Style]) -> some TextNode {
+    modifier(StyleModifier(styles: styles))
+  }
+}
+
+@usableFromInline
+struct StyleModifier<Content: TextNode>: NodeModifier {
+
+  @usableFromInline
+  let styles: [Style]
+
+  @usableFromInline
+  init(styles: [Style]) {
+    self.styles = styles
+  }
+
+  @usableFromInline
+  func render(content: Content) -> some TextNode {
+    styles.reduce(content.render()) {
+      $0.applyingStyle($1)
+    }
+  }
+}