Add MessageBox, SliderButton and ClickPanel

[Creator754915]

I add new UI component, and i developpe the Layout component

What i add ?

1. MessageBox
2. ClickPanel
3. Background

Messagebox

from ursina import *
from ursina.prefabs import MessageBox

app = Ursina()
messagebox = MessageBox(messagebox_name='My Messagebox', text='hello world!', scale=(.8, .5), color=color.azure,
                        text_origin=(-.36, .18))
messagebox.tooltip = Tooltip("MessageBox")

app.run()

Background

from ursina import *
from ursina.prefabs import Background
app = Ursina()

Background(texture='sky_sunset')

app.run()

ClickPanel

from ursina import *
from ursina.prefabs import ClickPanel
app = Ursina()

ClickPanel(key_control=False, key_bind="right mouse")

app.run()

[Creator754915]

Thank you !