Inputs: [data :- [s/Any] tgt :- s/Any]

Given an N-dim data structure (nested vectors/lists) & a target value, returns
a list of maps detailing where index values where the target value is found.

  (is= (find-idxs  [[ 1  2 3]
                    [10 11  ]
                    [ 9  2 8]]  2)
    [{:idxs [0 1], :val 2}
     {:idxs [2 1], :val 2}])