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.

1998/df/README.md

@@ -110,6 +110,17 @@ My first private version would only run when compiled on a Friday.
 I decided it would be better this way...
 These restrictions have been removed for your convenience.
 
+
+### 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.
+
+
+### How this entry works:
+
 The following lines describe how this program works; if you don't
 want to know it at this time, please skip them. If this entry would
 by some mistake win the contest, please do not rot13 this - I hate
@@ -118,9 +129,6 @@ reverse them. Anyone out there should have enough discipline and
 rot13 shouldn't be required, really. After all, we are not children
 anymore :-)
 
-
-## Obfuscation information:
-
 <hr style="width:10%;text-align:left;margin-left:0">
 
 This paragraph is not part of the author's remarks, but is a helpful

1998/df/index.html

@@ -480,6 +480,11 @@ some restrictions on the file name:</p>
 My first private version would only run when compiled on a Friday.
 I decided it would be better this way…
 These restrictions have been removed for your convenience.</p>
+<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="how-this-entry-works">How this entry works:</h3>
 <p>The following lines describe how this program works; if you don’t
 want to know it at this time, please skip them. If this entry would
 by some mistake win the contest, please do not rot13 this - I hate
@@ -487,7 +492,6 @@ rot13 spoilers since it is somewhat complicated on a Mac to
 reverse them. Anyone out there should have enough discipline and
 rot13 shouldn’t be required, really. After all, we are not children
 anymore :-)</p>
-<h2 id="obfuscation-information">Obfuscation information:</h2>
 <hr style="width:10%;text-align:left;margin-left:0">
 <p>This paragraph is not part of the author’s remarks, but is a helpful
 gift from the judges; if you read too fast to stop yourself, this should