add templates to hide push and pop for more idiomatic nim

[pietroppeter]

in p5js there is push and pop used for e.g. transforming coordinates or in general a temporary "mode" change. in nim it would be more idiomatic to define templates for common stuff, see for example (case of rotate or translate) Hugo advent 22 day 2 and usages below

probably a generic pushPop (or in other way named) template could be added too