dnsmap: add page (#8706)

* add dnsmap command

* csv file path is a variable

* Descriptions should start with a capital

* Description items should end with periods.

* invalid IP

* Update pages/linux/dnsmap.md

* fix typo and remove absolute paths

pages/linux/dnsmap.md

@@ -0,0 +1,20 @@
+# dnsmap
+
+> The dnsmap command scans a domain for common subdomains e.g. smtp.domain.org.
+> More information: <https://github.com/resurrecting-open-source-projects/dnsmap>.
+
+- Scan for subdomains using the internal wordlist:
+
+`dnsmap {{example.com}}`
+
+- Specify a list of subdomains to check for:
+
+`dnsmap {{example.com}} -w {{path/to/wordlist.txt}}`
+
+- Store results to a CSV file:
+
+`dnsmap {{example.com}} -c {{path/to/file.csv}}`
+
+- Ignore 2 IPs that are false positives (up to 5 possible):
+
+`dnsmap {{example.com}} -i {{123.45.67.89,98.76.54.32}}`