links: automatic command links are too lax now?

Should `dvc {cmd} {arg}` always be linked? E.g.:

> From https://dvc.org/doc/command-reference/repro#examples

I have the impression this was not the case before. It used to only do that for commands with subcommands, and perhaps some valid options of `dvc config`.

No source files or tests are named. Start by locating the automatic command-link handling in the Gatsby theme and compare its behavior with the referenced DVC command-reference example. Done means the intended linking rules for `dvc {cmd} {arg}`, subcommands, and valid `dvc config` options are established and covered by the relevant checks.

Written by the indexing model from the issue text.