feat: Add hashing color for cells (#93)

Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #93

doc/teapot.lyx

@@ -167,8 +167,8 @@ Copyright, Contributors and License
 teapot
 \noun default
  (Table Editor And Planner, Or: Teapot), is copyrighted 1995–2006 by Michael
- Haardt, and 2009–2010 by Jörg Walter, and 2019 by Glen Whitney, and is
- licensed under the Gnu General Public License v3 or later.
+ Haardt, and 2009–2010 by Jörg Walter, and 2019-2023 by Glen Whitney, and
+ is licensed under the Gnu General Public License v3 or later.
 \end_layout
 
 \begin_layout Standard
@@ -3994,9 +3994,13 @@ foreground
 \family sans
 background
 \family default
-() colors used to display a cell may be set.
- (Currently this only affects screen display.) The value of these attributes
- is a positive integer which acts as an index into the 
+() colors used to display a cell may be set and the
+\family sans
+ hashing
+\family default
+() color may be set as well.
+ (Currently this only affects screen display.) The value of each of these
+ attributes is a positive integer which acts as an index into the 
 \begin_inset Quotes eld
 \end_inset
 
@@ -8272,6 +8276,37 @@ is
  for example.
 \end_layout
 
+\begin_layout Description
+
+\series medium
+style
+\emph on
+
+\begin_inset space ~
+\end_inset
+
+
+\series default
+\emph default
+hashing
+\series medium
+(int
+\emph on
+
+\begin_inset space ~
+\end_inset
+
+
+\emph default
+c)
+\series default
+ evaluates to a style token with the hashing color set to 
+\emph on
+c
+\emph default
+ (and no other fields set).
+\end_layout
+
 \begin_layout Description
 hexact used as a keyword to the string() function; listed here to record
  that this identifier may not be used as a cell label.