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.

2012/kang/README.md

@@ -150,7 +150,15 @@ The design of the program explicitly allows for `EOF` even if it does not equal
 endian-independent.
 
 
-### Obfuscation
+### 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:
 
 Many obfuscations used are typical for standard IOCCC entries:
 

2012/kang/index.html

@@ -493,7 +493,11 @@ character set and two’s complement representation.</li>
 <code>-1</code> (it has to be negative per the standard but not necessarily <code>-1</code>) and both
 <code>signed char</code> and <code>unsigned char</code>, for example. Furthermore it is
 endian-independent.</p>
-<h3 id="obfuscation">Obfuscation</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="how-this-entry-works">How this entry works:</h3>
 <p>Many obfuscations used are typical for standard IOCCC entries:</p>
 <ul>
 <li>Two arguments from <code>main()</code> function are reused as normal variables.</li>