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.

2006/monge/README.md

@@ -154,8 +154,8 @@ Supported operations and functions are:
 
      +,-,*,/  | Arithmetic operations, priority of  * , /  over  +,-  is respected.
      <,>      | Compares the real parts of two complex numbers (the imaginary part
-     	      | is ignored). Any number of conditions is allowed, the iteration will
-	      | just stop as soon as one of them fails.
+              | is ignored). Any number of conditions is allowed, the iteration will
+              | just stop as soon as one of them fails.
      Abs2     | Calculates the squared norm, i.e.: Abs2(a+b*i) is (a*a+b*b)+0*i.
      Re       | Extract the real part, i.e.: Re(a+b*i) is a+0*i.
      Im       | Extract the imaginary part, i.e.: Im(a+b*i) is b+0*i.

2006/sykes1/README.md

@@ -60,17 +60,17 @@ This was done on a Rocky Linux 9.2 server with `Intel(R) Core(TM) i9-9900K CPU @
 3.60GHz` with 16 cores (via HyperThreading):
 
 ```
-    real	6m35.524s
-    user	6m35.159s
-    sys		0m0.002s
+    real        6m35.524s
+    user        6m35.159s
+    sys         0m0.002s
 ```
 
 and done with macOS Sonoma with the Max M1 chip:
 
 ```
-    real	7m10.786s
-    user	7m8.322s
-    sys		0m0.110s
+    real        7m10.786s
+    user        7m8.322s
+    sys         0m0.110s
 ```
 
 
@@ -180,8 +180,8 @@ the start of the program:
 
 ``` <!---c-->
     int s[ ] = { 186, 94, 1426, 3098
-	    ,1047 , 122 , 1082 , 3083 , 1039
-	    , 569 , 527 , 1054 , 531  }  ;
+            ,1047 , 122 , 1082 , 3083 , 1039
+            , 569 , 527 , 1054 , 531  }  ;
 ```
 
 Each piece is a bitmap, and represents a 3x3x3 cube.