It's Not possible to install it with R < 4.0

[gaspare-mattarella]

As long as this package will depend on rjson it won't be possible to install it on R < 4 since rjson is not available anymore for R < 4.

> install.packages('rjson')
Installing package into ‘C:/R/R-3.6.1/packages’
(as ‘lib’ is unspecified)
Warning in install.packages :
  package ‘rjson’ is not available (for R version 3.6.1)

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