Update README.md (tim poke)

Merge branch 'main' of https://github.com/jon-gilbert/openscad_pvc into main

doc update, synopsis added

Update README.md

tim poke

cyl() argument 'l=' flipped to 'h='

added sucess only conditional

minor removeal of 'externals', done some time ago

make sure objects are loadable

generatedocs

yaml indenting just acting like python indenting

minor doc update staged for a unit-test and documentation rebuild

"make tests", not "make test"

Create makefile-unit-tests.yml

cleanup; adding the header scad