Only update the camera if called from the same world

Do not shake if delta time is 0

Fixes #72

Update README.md

Updated docs

fix: check for GO existence before sending message (#80)

The camera was calling `msg.post(sender, MSG_SHAKE_COMPLETED) without
checking if sender is still present at that point. Since this is a
callback, the shake can end at a point in time where the sender is no
longer alive.

Sample error produced when this happens below :
`ERROR:GAMEOBJECT: Instance '/instance80' could not be found when
dispatching message 'shake_completed' sent from game:/camera#script`

Co-authored-by: berru <berru@riseup.net>

Removed set_window_scaling_factor from docs

Updated camera.lua (#73)

Sorted a issue where it used DISPLAY_WIDTH instead of DISPLAY_HEIGHT for vertical camera shaking

Co-authored-by: Mobjunk <34821598+Mobjunk@users.noreply.github.com>

Check window width and height in render script

Fixes #68

Add world_to_window function (#64)

Set stencil mask