improved indentation and whitespace for markdown code blocks

All code blocks in markdown have been intended by at least 4 spaces.

We add `--tab-stop=8` to all `pandoc(1)` executions in order to set
a better tab stop indentation, especially for tab intended code blocks.

Changed `bin/pandoc-wrapper.sh` VERSION from "1.5.3 2024-03-26"
to "1.6 2024-03-31".

Fixed `1991/brnstnd/sorta.README.md` so that the sorta code
is code blocks.

Removed unneeded paragraph group in copyright in `inc/footer.default.html`.

Fixed excess whitespace after list Author on entry `index.html` page.

Changed `bin/output-index-author.sh` VERSION from "1.5.2 2024-03-26"
to "1.6 2024-03-31".

Performed `make www` to perform the above and test under macOS.

TODO: Fix the problem of the initial line of code being extra intended.
TODO: Fix excess whitespace around code that is inline.

2018/bellard/README.md

@@ -1,7 +1,7 @@
 ## To build:
 
 ```sh
-make
+    make
 ```
 
 There is an alternate version that should work with Windows. See [Alternate
@@ -11,7 +11,7 @@ code](#alternate-code) below.
 ## To use:
 
 ```sh
-./prog > lena.ppm
+    ./prog > lena.ppm
 ```
 
 
@@ -22,7 +22,7 @@ running the above command (`./prog > lena.ppm`), open `lena.ppm` in your
 graphics viewer of choice.  After that try:
 
 ```sh
-./try.sh
+    ./try.sh
 ```
 
 NOTE: the script uses the tools `pngtopam(1)` (or `pngtopnm(1)` for older
@@ -45,7 +45,7 @@ for Windows.
 ### Alternate build:
 
 ```sh
-make alt
+    make alt
 ```
 
 
@@ -100,9 +100,9 @@ it accepts to decompress image files from its standard
 input. Examples:
 
 ```sh
-./prog d < lena512.bin > lena512.ppm
-./prog d < fruits.bin > fruits.ppm
-./prog d < vintage_cars.bin > vintage_cars.ppm
+    ./prog d < lena512.bin > lena512.ppm
+    ./prog d < fruits.bin > fruits.ppm
+    ./prog d < vintage_cars.bin > vintage_cars.ppm
 ```
 
 The original images for [fruits][1] and [vintage cars][2] come from