Create update-lit.sh

[Be1zebub]

Bash script that runs get-lit.sh when lit/luvi/luvit is not installed or not updated.

I wrote this to create luvit docker image for pterodactyl with auto-updating feature.

I made it dependent on get-lit.sh, without worrying about the fact that "when one component needs update, it will update all" - due to the fact that the luvit is very small, the execution get-lit.sh takes no more than a few seconds on any machine.

[Be1zebub]

[Bilal2453]

I am also not entirely sure if we really need such script in the repo. While I am sure it will be useful for someone out there, internally I see no use for it, the only reason we have get-lit is the install script; it is the main way for anyone to get Luvit/Lit/Luvi.

So unless there is an internal usage for this script, I am not entirely sure if we want it here.