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.

2001/jason/README.md

@@ -117,7 +117,15 @@ the game entertaining, see if you can find
 in the source code.)
 
 
-### GAME STRATEGY 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 via the source.
+
+If you get stuck, come back and read below for additional hints and information.
+
+
+### GAME STRATEGY
 
 The trick, of course, is to drop items in empty rooms to mark them.  That way
 you usually know if you're in a room you've seen before.  It greatly aids

2001/jason/index.html

@@ -481,7 +481,11 @@ the game entertaining, see if you can find</p>
 <pre><code>    the fish scales              Q)++j&lt;
     the shooting star         -~- ~ -~i +</code></pre>
 <p>in the source code.)</p>
-<h3 id="game-strategy-spoiler">GAME STRATEGY SPOILER</h3>
+<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge</h3>
+<p><strong>If you want a greater challenge, don’t read any further</strong>:
+just try to understand the program via the source.</p>
+<p>If you get stuck, come back and read below for additional hints and information.</p>
+<h3 id="game-strategy">GAME STRATEGY</h3>
 <p>The trick, of course, is to drop items in empty rooms to mark them. That way
 you usually know if you’re in a room you’ve seen before. It greatly aids
 mapping.</p>