doc: improve dns introduction
The introductory paragraphs for the dns
module do not explain what the
module is for. Add a short (two brief sentences) explanation.
It also emphasizes that functions in the dns module are divided into two categories, but that there is only one function in one of the categories, making the whole categories thing a bit odd to emphasize. Keep the material about the distinctions without discussing categories.
There are other incidental revisions (changing an example IP to
example.org
and so on).
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines