fix: enable text selection and copy/paste in RichView

Added .textSelection(.enabled) modifier to Text view in RichView to allow
users to select and copy text content. This enables standard iOS text
selection gestures (long press, drag to select) and copy/paste functionality.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: graycreate

V2er/Sources/RichView/Views/RichView.swift

@@ -69,6 +69,7 @@ public struct RichView: View {
                 Text(attributedString)
                     .font(.system(size: configuration.stylesheet.body.fontSize))
                     .lineSpacing(configuration.stylesheet.body.lineSpacing)
+                    .textSelection(.enabled)
                     .environment(\.openURL, OpenURLAction { url in
                         onLinkTapped?(url)
                         return .handled