Change design block file ext to kicad_block[s]
Fully include design blocks in project archives
schematic design blocks are a .kicad_blocks folder (library), containing
a .kicad_block folder (block), containing a .kicad_sch file (schematic
fragment) and a .json file (metadata). The .kicad_sch file is already
covered in the archived extension list, but the json needs to be
included.
As a side effect, this will pick up any other json file in the project
directory.
Also archive design block library tables
