Expand all leading tabs in markdown files

Given how problematic leading tabs in markdown files can be,
we have expanded all leading tabs in markdown files by:

```sh
find * -type f -name '*.md' -print |
  while read -r file; do
    rm -f "$file.tmp" ;
    expand < "$file" > "$file.tmp" ;
    mv -f -v "$file.tmp" "$file" ;
  done
```

Given the previous changes to `bin/pandoc-wrapper.sh` and other recent
commits and recent pull requests, the were were **NO** changes to
any HTML files.  This is a **good thing** as the expression goes.

No there are no leading tabs in any markdown files.
A check to catch any re-introduction of leading tabs
into any markdown file is on the way.

BTW: We do not have anything against leading tabs in files,
even though we have had to deal with their impact on forming
HTML from markdown files (as well as the calc source code).
It is just that this is one of those cases where tabs conflict
(sometimes caused by people wanting to change the classic
8-space tab model) with a desired outcome.

Perform `make www` to perform the above and test under macOS.

1993/rince/README.md

@@ -126,9 +126,9 @@ must move after firing to be able to fire again.
 
 ### Keys
 
-- `j`	-	    Left
-- `l`	-	    Right
-- `k`	-	    Fire
+- `j`   -           Left
+- `l`   -           Right
+- `k`   -           Fire
 
 This is a new breed of generic games. For instance:
 

1993/rince/design.md

@@ -10,9 +10,9 @@ For instance, assume you wish to make a boulder `o` roll off a hill `/`
 A standard automata would have 2 rules something like this:
 
 ```
-    o..			...
-    \..  -->  'o'		.o.  -->  '.'
-    ...			.\.
+    o..                 ...
+    \..  -->  'o'               .o.  -->  '.'
+    ...                 .\.
 ```
 
 However, the system I devised, in order to keep things small and neat(!),
@@ -20,9 +20,9 @@ was to define a 3x3 to 3x3 map (instead of the 3x3 to 1x1 shown above).
 Hence:
 
 ```
-    .o.	  ...
+    .o.   ...
     .\.  -->  .\o
-    ...	  ...
+    ...   ...
 ```
 
 This does of course have the odd problem with clashes. What if we want to roll
@@ -32,9 +32,9 @@ transition has priority win. Such a case may produce the following change of
 maps (depending on which 'roll' transition is used first).
 
 ```
-    o.o			..o	    o..
-    \./	  changes to	\o/  or to  \o/
-    ...			...	    ...
+    o.o                 ..o         o..
+    \./   changes to    \o/  or to  \o/
+    ...                 ...         ...
 ```
 
 I claim that it is possible to perform all of the 3x3 to 1x1 transitions in a
@@ -59,9 +59,9 @@ is hit we have a transition like:
 ## Key: l
 
 ```
-    * * *		* * *
-    * @ .		* . @
-    * * *		* * *
+    * * *               * * *
+    * @ .               * . @
+    * * *               * * *
 ```
 
 Here I also use wildcards. On the match side (left) of the transition, an
@@ -73,9 +73,9 @@ purposes of space saving, this transition is shrunk to a single line.
 ## Key: K
 
 ```
-    a b c		1 2 3
-    d e f		4 5 6
-    g h i		7 8 9
+    a b c               1 2 3
+    d e f               4 5 6
+    g h i               7 8 9
 ```
 
 is written as: `eabcdfghi512346789K`.