Add two manual pages in bsdinstall section

PR:             253875
Submitted by:   bruce.lilly (AT) gmail.com

documentation/content/en/books/handbook/bsdinstall/_index.adoc

@@ -201,7 +201,11 @@ This example uses [.filename]#/dev/da0# as the target device where the image wil
 # dd if=FreeBSD-12.1-RELEASE-amd64-memstick.img of=/dev/da0 bs=1M conv=sync
 ....
 +
-If this command fails, verify that the USB stick is not mounted and that the device name is for the disk, not a partition. Some operating systems might require this command to be run with . The syntax varies slightly across different platforms; for example, Mac OS(R) requires a lower-case `bs=1m`. Systems like Linux(R) might buffer writes. To force all writes to complete, use .
+If this command fails, verify that the USB stick is not mounted and that the device name is for the disk, not a partition.
+Some operating systems might require this command to be run with man:sudo[8].
+The syntax varies slightly across different platforms; for example, Mac OS(R) requires a lower-case `bs=1m`.
+Systems like Linux(R) might buffer writes.
+To force all writes to complete, use man:sync[8].
 ****
 
 [.procedure]