docs: mention that color rules are applied in the order they are listed

Suggested-by: Tiago Almeida <tjamadeira@gmail.com>

doc/nano.texi

@@ -1077,6 +1077,9 @@ stronger highlight.
 If your terminal supports transparency, not specifying a "bgcolor"
 tells @command{nano} to attempt to use a transparent background.
 
+All coloring commands are applied in the order in which they are specified,
+which means that later commands can recolor stuff that was colored earlier.
+
 @item icolor @var{fgcolor},@var{bgcolor} "@var{regex}" @dots{}
 Same as above, except that the matching is case insensitive.
 

doc/nanorc.5

@@ -411,6 +411,9 @@ one of which must be specified.  Valid color names are:
 You may use the prefix \fBbright\fR for the foreground color to get a
 stronger highlight.  If your terminal supports transparency, not specifying
 a \fIbgcolor\fP tells \fBnano\fP to attempt to use a transparent background.
+.sp
+All coloring commands are applied in the order in which they are specified,
+which means that later commands can recolor stuff that was colored earlier.
 .TP
 .BI "icolor " fgcolor , bgcolor " """ regex """ " \fR...
 Same as above, except that the matching is case insensitive.

doc/sample.nanorc.in

@@ -238,6 +238,9 @@
 ## yellow, magenta, cyan.  For foreground colors, you may use the
 ## prefix "bright" to get a stronger highlight.
 ##
+## All color commands are applied in the order in which they are specified,
+## meaning that later commands can recolor stuff that was colored earlier.
+##
 ## All regexes (regular expressions) are of the extended type (ERE).
 ##
 ## To use multi-line regexes, use the start="regex" end="regex"