To/FromJSON instance

[picca]

It would be great if we could serialize unserialize via Aeson dimensionnal values.

for now we have this.

• No instance for (FromJSON
                     (dimensional-1.0.1.3:Numeric.Units.Dimensional.Internal.Dimensional
                        'Numeric.Units.Dimensional.Variants.DQuantity
                        Numeric.Units.Dimensional.Dimensions.TypeLevel.DLength
                        Double))
    arising from a use of ‘aeson-1.2.4.0:Data.Aeson.Types.FromJSON.$dmparseJSON’

thanks for considering

[bjornbm]

I have no objections but would appreciate a patch if you want it sooner rather than later (I guess it already is “later” – sorry). I'm thinking it will have to rely on Numeric.Units.Dimensional.Dynamic and should probably go in dimensional-dk-experimental or a package of its own.

[LaurentRDC]

If someone wants to work on this, this PR can be used as a template: #224