add notices to those who wish for a greater challenge

We add the following level-3 header to help people identify text
they may wish to skip if they wish for a greater challenge:

```
```

After that notice we add:

```
**If you want a greater challenge, don't read any further**:
just try to understand the program via the source.

If you get stuck, come back and read below for additional hints and information.
```

And sometimes follow with:

```
```

Or sometimes follow with:

```
```

Where the alt code impacts a "greater challenge", we add instead:

```
**If you want a greater challenge, don't read any further**:
just try to understand the program without looking at the Alternate code.

If you get stuck, come back and look at the Alternate code.
```

And where a given command impacts a "greater challenge", we add instead:

```
**If you want a greater challenge, don't read any further**:
just try to understand the program without running the command below.

If you get stuck, come back and run the following command:
```

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

1996/huffman/README.md

@@ -32,12 +32,18 @@ For more detailed information see [1996/huffman in bugs.html](../../bugs.html#19
 
 ## Judges' remarks:
 
-If you are still confused and want to read a spoiler, check out
+If you are still confused, check out
 the source and it will be clear as mud!
 
 And for a misleading hint, consider who won!  :-)
 
-And if you really can't see what is going on, here is an extra spoiler:
+
+### NOTICE to those who wish for a greater challenge
+
+**If you want a greater challenge, don't read any further**:
+just try to understand the program without running the command below.
+
+If you get stuck, come back and run the following command:
 
 ``` <!---sh-->
     ./huffman < huffman.c 2>/dev/null