Import multiple boards

[christophenne]

Alternatively to only one file, input a directory containing multiple json files that should be imported into the same project.

[christophenne]

Could simply be achieved with a loop over the desired json files in bash/powershell/anything else, so I won't implement it.

Example in bash:

for file in `ls -a my-boards/*.json`; do npm run import-board -- --file=$file;  done;