Customizable Wall Shelf Bracket - openscad

This is a remix of Customizable L-Corner Bracket | Shelf Bracket by @MatthewGhost - the remix includes changes in the code adding configurable countersinks and hole positions, allowing for precise screw placement and a secure fit in various materials. I didn't take anything from Fully Customizable Wall Shelf Bracket but searching MW for Openscad Shelf Bracket I found it, so I just list it here as a remix so it will not be reported for being a one not listing it. Basically it also has fully a