Guidebook tweaks for ^E, section 5 header

Describe #wizdetect as revealing hidden things rather than searching
for hidden things since the latter is described more than once as
possibly needing multiple tries.

For plain text output, the "Rooms and corridors" section header was
harder than necessary to notice because it seemed to run together
with the list of commands preceding it.
|
| u    #untrap
|
| 5.  Rooms and corridors
|
Inserting an extra blank line in between them is helpful.  That isn't
needed for Postscript/PDF output because the text of the section
title is rendered with bold font, but I didn't attempt to make the
extra line be conditional.  The 'roff directive is added as a comment
to the TeX source without knowing whether an extra blank line would
be useful there (doubtful).

doc/Guidebook.mn

@@ -35,7 +35,7 @@
 .ds vr "NetHack 3.7
 .ds f0 "\*(vr
 .ds f1
-.ds f2 "July 27, 2021
+.ds f2 "August 26, 2021
 .
 .\" A note on some special characters:
 .\" \(lq = left double quote
@@ -1637,8 +1637,9 @@ Bury objects under and around you.
 Autocompletes.
 Debug mode only.
 .lp #wizdetect
-Search for hidden things (secret doors or traps or unseen monsters)
+Reveal hidden things (secret doors or traps or unseen monsters)
 within a modest radius.
+No time elapses.
 Autocompletes.
 Debug mode only.
 Default key is \(oq\(haE\(cq.
@@ -1802,6 +1803,7 @@ option is on, some additional letter commands are available:
 .lp u
 #untrap
 .
+.BR 1 \"blank line for extra separation; plain text output looks better
 .hn 1
 Rooms and corridors
 .pg