[examples] resize fixes

[jopadan]

changes

• fix screen size not being updated at window resize event
• fix size dependent font/rectangle/object draw

example bug list

• [examples] List of examples not working properly on Web platform #4682
• same for other platforms

To reproduce just maximize the example window
shaders_postprocessing

shaders_postprocessing fixed

[raysan5]

@jopadan Please, could you provide some comparison images to illustrate the issues those changes are addressing? Those are many examples changes and I'm not sure if so many reviews are required, considering they seem to be targeted for a single platform.

[jopadan]

@raysan5 Added images for one example. There are no platform dependent changes in the PR.

[jopadan]

Is there any chance of getting a response?

[raysan5]

@jopadan As I told you those are too many changes for a single PR. I need some time to review them properly. Still wondering why all those changes are required.

[jopadan]

@raysan5 All these changes are required and only in examples to fix none adaptive viewport resize/gui element positions.
There are unnecessary calls to GetScreenWidth()/GetScreenHeight() that should be avoided adding event callbacks in order to circumvent performance penalties generated in loops.