bulk run and image creation

[eXpire163]

Hi,

i really appriciate that you have created an openscad action.

For most of the time i use openscad cli to create images out of my files to create a repo gallery.

Therefor it would be nice two be able to pass in multiple files or a directory.

When using openscad on github runners it cannot create images as it requires a xServer. Xvfb can solve this.

I will post a PR in a minute that might solve these topics

[eXpire163]

a sample output can look like this: https://github.com/eXpire163/openSCAD

[flat35hd99]

Thank you for your suggestions, @eXpire163

it would be nice to be able to pass in multiple files or a directory.

It is nice idea. I'm checking your PR #6