add instruction for how to merge >1 json?

[jayoung]

One thing it took me a minute to figure out is what to do when I have >1 json file. We need to concatenate them for validation (the workflow submission allows you to upload >1 json, but the validation doesn't)

Here's a note I wrote for myself. Could maybe add something like this somewhere in WDL101. Not sure where the best spot for it would be.

To merge two or more json files from the command line, we can use jq

jq -s '.[0] * .[1]' file1.json file2.json > combined.json
jq -s '.[0] * .[1] * .[2]' file1.json file2.json file3.json > combined.json

Maybe there's a better way - I would hope there's a more generalized solution where you don't need to mess with the bit in quotes when you change the number of files you're merging.