docs: document the new -O/--bookstyle and 'set bookstyle' options

doc/nano.1

@@ -155,6 +155,10 @@ hard-wrapping occurs or when text is justified.
 .BR \-N ", " \-\-noconvert
 Disable automatic conversion of files from DOS/Mac format.
 .TP
+.BR \-O ", " \-\-bookstyle
+When justifying, treat any line that starts with whitespace as the
+beginning of a paragraph (unless auto-indenting is on).
+.TP
 .BR \-P ", " \-\-positionlog
 For the 200 most recent files, log the last position of the cursor,
 and place it at that position again upon reopening such a file.

doc/nano.texi

@@ -239,6 +239,11 @@ hard-wrapping occurs or when text is justified.
 @itemx --noconvert
 Disable automatic conversion of files from DOS/Mac format.
 
+@item -O
+@itemx --bookstyle
+When justifying, treat any line that starts with whitespace as the
+beginning of a paragraph (unless auto-indenting is on).
+
 @item -P
 @itemx --positionlog
 For the 200 most recent files, log the last position of the cursor,
@@ -768,6 +773,10 @@ function tags, line numbers, and selected text.  This is overridden by
 setting the options @code{titlecolor}, @code{statuscolor}, @code{keycolor},
 @code{functioncolor}, @code{numbercolor}, and/or @code{selectedcolor}.
 
+@item set bookstyle
+When justifying, treat any line that starts with whitespace as the
+beginning of a paragraph (unless auto-indenting is on).
+
 @item set brackets "@var{characters}"
 Set the characters treated as closing brackets when justifying
 paragraphs.  This may not include blank characters.  Only closing

doc/nanorc.5

@@ -100,6 +100,10 @@ function tags, line numbers, and selected text.  This can be overridden by
 setting the options \fBtitlecolor\fP, \fBstatuscolor\fP, \fBkeycolor\fP,
 \fBfunctioncolor\fP, \fBnumbercolor\fP, and \fBselectedcolor\fP.
 .TP
+.B set bookstyle
+When justifying, treat any line that starts with whitespace as the
+beginning of a paragraph (unless auto-indenting is on).
+.TP
 .BI "set brackets """ characters """
 Set the characters treated as closing brackets when justifying
 paragraphs.  This may not include blank characters.  Only closing

doc/sample.nanorc.in

@@ -30,6 +30,9 @@
 ## Use bold text instead of reverse video text.
 # set boldtext
 
+## Treat any line with leading whitespace as the beginning of a paragraph.
+# set bookstyle
+
 ## The characters treated as closing brackets when justifying paragraphs.
 ## This may not include any blank characters.  Only closing punctuation,
 ## optionally followed by these closing brackets, can end sentences.