dnswalk: add page (#16968)

Co-authored-by: Managor <42655600+Managor@users.noreply.github.com>
Co-authored-by: Juri Dispan <juri.dispan@posteo.net>
Co-authored-by: Dylan <145150333+dmmqz@users.noreply.github.com>

pages/common/dnswalk.md

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+# dnswalk
+
+> DNS debugger.
+> "Walk" across zones and validate database consistency and best practices.
+> More information: <https://manned.org/dnswalk>.
+
+- Debug a DNS pathway for a Fully Qualified Domain Name (FQDN):
+
+`dnswalk {{domain}}.`
+
+- Process sub-domains [r]ecursively:
+
+`dnswalk -r {{domain}}.`
+
+- Only perform a `dnswalk` if the zone has been [m]odified since the last run:
+
+`dnswalk -m {{domain}}.`
+
+- Print [d]ebugging and status information to `stderr` instead of `stdout`:
+
+`dnswalk -d {{domain}}.`
+
+- Suppress the check for [i]nvalid characters in the domain name:
+
+`dnswalk -i {{domain}}.`
+
+- Enable duplicate A record warnings:
+
+`dnswalk -a {{domain}}.`
+
+- Enable "[F]ascist checking" to compare the A record PTR name with the forward name and report mismatches:
+
+`dnswalk -F {{domain}}.`
+
+- Enable "[l]ame delegation" to test whether the listed host is returning authoritative answers:
+
+`dnswalk -l {{domain}}.`