docs: adjust for the enhancement of the default quoting regex

doc/nano.1

@@ -127,7 +127,7 @@ and place it at that position again upon reopening such a file.
 .BR "\-Q ""\fIregex\fB""" ", " "\-\-quotestr=""" \fIregex """
 Set the regular expression for matching the quoting part of a line.
 This is used when justifying.
-The default value is \fB"^([\ \\t]*([#:>|}]|//))+"\fP.
+The default value is \fB"^([\ \\t]*([!#%:;>|}]|//|--))+"\fP.
 Note that \fB\\t\fP stands for an actual Tab.
 .TP
 .BR \-R ", " \-\-restricted

doc/nano.texi

@@ -222,7 +222,7 @@ and place it at that position again upon reopening such a file.
 @item -Q "@var{regex}"
 @itemx --quotestr="@var{regex}"
 Set the regular expression for matching the quoting part of a line, used
-when justifying.  The default value is @t{"^([@w{ }\t]*([#:>|@}]|//))+"}.
+when justifying.  The default value is @t{"^([@w{ }\t]*([!#%:;>|@}]|//|--))+"}.
 Note that @code{\t} stands for a literal Tab character.
 
 @item -R
@@ -832,7 +832,7 @@ keystroke instead of 25.  Note that @option{constantshow} overrides this.
 @item set quotestr "@var{regex}"
 The email-quote string, used to justify email-quoted paragraphs.  This
 is an extended regular expression.  The default value is
-@t{"^([@w{ }\t]*([#:>|@}]|//))+"}.
+@t{"^([@w{ }\t]*([!#%:;>|@}]|//|--))+"}.
 Note that @code{\t} stands for a literal Tab character.
 
 @item set rawsequences

doc/nanorc.5

@@ -198,7 +198,7 @@ keystroke instead of 25.  The option \fBconstantshow\fR overrides this.
 .B set quotestr "\fIregex\fP"
 The email-quote string, used to justify email-quoted paragraphs.  This
 is an extended regular expression.  The default value is
-"\fB^([\ \\t]*([#:>|}]|//))+\fP".  Note that \fB\\t\fR stands for an actual
+"\fB^([\ \\t]*([!#%:;>|}]|//|--))+\fP".  Note that \fB\\t\fR stands for an actual
 Tab character.
 .TP
 .B set rawsequences

doc/sample.nanorc.in

@@ -124,7 +124,7 @@
 
 ## The email-quote string, used to justify email-quoted paragraphs.
 ## This is an extended regular expression.  The default is:
-# set quotestr "^([ 	]*([#:>|}]|//))+"
+# set quotestr "^([ 	]*([!#%:;>|}]|//|--))+"
 
 ## Try to work around a mismatching terminfo terminal description.
 # set rawsequences