Create development website

[peterdesmet]

When we are working on Data Package v2 support in frictionless-r, it will be useful to have a rendered pkgdown website (to preview) changes, without it replacing the pkgdown website of the released version of frictionless-r. This will especially be useful for the vignettes: #226

This can be done development: mode: auto in pkgdown: https://pkgdown.r-lib.org/reference/build_site.html#development-mode