fix HTML problems related to pandoc and markdown image notation

Improve `make clobber` for `2004/anonymous`.

Instead of using this markdown element to embed an image:

```
![alt text](filename.png "Title")
```

Use a "img" HTML element with "alt", "alt", "width" and "length"
attributes:

```
<img src="filename.png"
 alt="describe the filename.png image for someone who cannot view it"
 width=PIXEL_WIDTH height=PIXEL_HEIGHT>
```

This was performed for:

```
2004/anonymous/index.html
2005/boutines/index.html
2011/goren/index.html
2012/vik/index.html
2013/birken/index.html
2013/cable1/index.html
2013/cable3/index.html
2013/hou/doc/example.html
2013/hou/index.html
2020/ferguson1/chocolate-cake.html
```

In the case of `2013/cable1/index.html` we reduce the displayed
image size by a factor for 2.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

In the case of `2013/hou/index.html` we reduce the displayed
image size by a factor for 2.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

In the case of `2020/ferguson1/chocolate-cake.html` we reduce the displayed
image size by a factor for 4.  There is **NO** need to downsize the image
as this image size reduction produces a clean and sharp looking image.

Run `make www` to perform the above.

2013/cable1/README.md

@@ -65,18 +65,20 @@ A PC guy as expected.  What about that other Steve?
 Humm .. maybe there is a hidden reason he is leaving the late Micro$oft? :-)
 Why late? Because:
 
-![tweet about M$ being dead](dead-ms-tweet.jpg)
+<img src="dead-ms-tweet.jpg"
+ alt="image of snarky tweet from 2013 Nov 15 by Landon Noll about Microsoft"
+ width=491 height=312>
 
--=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
-An important 2023 update about twitter:
+```
+    An important 2023 update about twitter:
 
-The IOCCC no longer uses twitter.  Today the IOCCC uses Mastodon.
-For more information and to see our IOCCC Mastodon posts, see:
+    The IOCCC no longer uses twitter.  Today the IOCCC uses Mastodon.
+    For more information and to see our IOCCC Mastodon posts, see:
 
-    https://fosstodon.org/@ioccc
+	https://fosstodon.org/@ioccc
 
-End of important 2023 update to this historic note.
--=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+    End of important 2023 update to this historic note.
+```
 
 So how does a one line C source know so much?  Hint: it doesn't.
 

2013/cable1/index.html

@@ -177,17 +177,17 @@ testing:</p>
 <pre><code>    ./cable1 Ballmer Mac PC</code></pre>
 <p>Humm .. maybe there is a hidden reason he is leaving the late Micro$oft? :-)
 Why late? Because:</p>
-<figure>
-<img src="dead-ms-tweet.jpg" alt="tweet about M$ being dead" />
-<figcaption aria-hidden="true">tweet about M$ being dead</figcaption>
-</figure>
-<p>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
-An important 2023 update about twitter:</p>
-<p>The IOCCC no longer uses twitter. Today the IOCCC uses Mastodon.
-For more information and to see our IOCCC Mastodon posts, see:</p>
-<p>https://fosstodon.org/<span class="citation" data-cites="ioccc">@ioccc</span></p>
-<p>End of important 2023 update to this historic note.
--=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-</p>
+<p><img src="dead-ms-tweet.jpg"
+ alt="image of snarky tweet from 2013 Nov 15 by Landon Noll about Microsoft"
+ width=491 height=312></p>
+<pre><code>    An important 2023 update about twitter:
+
+    The IOCCC no longer uses twitter.  Today the IOCCC uses Mastodon.
+    For more information and to see our IOCCC Mastodon posts, see:
+
+        https://fosstodon.org/@ioccc
+
+    End of important 2023 update to this historic note.</code></pre>
 <p>So how does a one line C source know so much? Hint: it doesn’t.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="presidents-of-the-united-states-of-america">Presidents of the United States of America!</h3>