Mixed up use of Top/Left Bottom/Right in JoinHorizontal and JoinVertical calls

[shaunco]

These JoinHorizontal calls should use lipgloss.Top or lipgloss.Bottom rather than lipgloss.Left or lipgloss.Right:

• https://github.com/charmbracelet/lipgloss/blob/87dd58def709590a169ba141d22ab1c76081275e/internal/tree/renderer.go#L100

These JoinVertical calls should use lipgloss.Left or lipgloss.Right rather than lipgloss.Top or lipgloss.Bottom:

• https://github.com/charmbracelet/lipgloss/blob/87dd58def709590a169ba141d22ab1c76081275e/internal/tree/renderer.go#L84
• https://github.com/charmbracelet/lipgloss/blob/87dd58def709590a169ba141d22ab1c76081275e/internal/tree/renderer.go#L91
• https://github.com/charmbracelet/lipgloss/blob/87dd58def709590a169ba141d22ab1c76081275e/internal/tree/renderer.go#L129

[bashbunni]

Thank you! This is fixed in #342 will link this issue to that PR so it'll close once merged :)