Add option to Justify

[naveen521kk]

It isn't that great that we can't justify a Paragraph of Text directly in Manim using MarkupText. Also, there is a Paragraph Mobject but it does things manually which Pango does for us. Also, we should make Paragraph object use these rather than implementing it by hand, as it is done currently.
these are the link to docs which we should implement
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-set-justify
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-set-indent
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-set-spacing
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-set-line-spacing
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-set-auto-dir
https://developer.gnome.org/pango/stable/pango-Layout-Objects.html#pango-layout-set-alignment
This should be done after #30
cc @PhilippImhof

[naveen521kk]

I have done some in 942f2f6
where I could create things like, center justified

or like this, right justified

or with an indent in the start

or justified