Make adding links to docs.ropensci.org part of approval template

[noamross]

Adding docs.ropensci.org as URL and such should be part of the approval template. Since there's some information about this in the FAQ that @jeroen sent to package authors, we should add this somewhere in the dev guide so that we can link to it.

[maelle]

Related to #162 (that did not add all the elements mentioned above)

[maelle]

Or maybe it did 🤔

[maelle]

@sckott might be good to have this in the current milestone as part of the changes related to docs?

[sckott]

sounds good