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.

2020/ferguson1/chocolate-cake.html

@@ -144,10 +144,9 @@ below is after it’s been iced. The image <a href="ioccc-cake.jpg">ioccc-cake.j
 feeble attempt at drawing <code>IOCCC</code> into the cake before icing, a different time.
 The picture below was taken for my birthday (14 February) in 2022 as it’s the
 best one I have:</p>
-<figure>
-<img src="cake.jpg" alt="picture of the Double-layered chocolate fudge cake" />
-<figcaption aria-hidden="true">picture of the Double-layered chocolate fudge cake</figcaption>
-</figure>
+<p><img src="cake.jpg"
+ alt="photograth of a delicious double-layered chocolate fudge cake"
+ width=756 height=602></p>
 <p>There are two sets of ingredients and instructions; the cake and the icing. In
 addition there are some <strong>VERY IMPORTANT NOTES</strong> to pay attention to; some will
 be repeated because they’re <strong>VITALLY IMPORTANT</strong> for the quality of the cake.

2020/ferguson1/chocolate-cake.md

@@ -11,7 +11,9 @@ feeble attempt at drawing `IOCCC` into the cake before icing, a different time.
 The picture below was taken for my birthday (14 February) in 2022 as it's the
 best one I have:
 
-![picture of the Double-layered chocolate fudge cake](cake.jpg)
+<img src="cake.jpg"
+ alt="photograth of a delicious double-layered chocolate fudge cake"
+ width=756 height=602>
 
 There are two sets of ingredients and instructions; the cake and the icing. In
 addition there are some **VERY IMPORTANT NOTES** to pay attention to; some will