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.

2004/gavin/gavin.md

@@ -15,12 +15,14 @@ on half a dozen machines or so, and worked on all but one.  The failure came in
 the form of the machine rebooting itself midway through loading the OS, with no
 nasty side-effects.
 
+```
     Hardware requirements - i386 or better processor, but the GUI is
     surprisingly power-hungry, so I would recommend a fast P3 or P4 processor
     (has been tested on P3/P4/Athlon machines).  Minimum RAM is something like
     32MB.  PS/2 mouse & keyboard required - no USB I'm afraid, and the keyboard
     map is for a UK keyboard.  Uses VESA VBE 3.0, so should work on any modern
     graphics card (has been tested on NVIDIA, Matrox, and SiS cards).
+```
 
 3. Now you need to setup a bootloader to load the OS.  If you have a system
 using a lilo bootloader you can simply add the OS to your boot menu.  Just add
@@ -30,10 +32,12 @@ If you do not wish modify your lilo setup, one easy option is to get yourself a
 GRUB boot disk image, and follow the instructions for GRUB below - Debian users
 can simply run`apt-get install grub-disk` to get themselves a GRUB boot disk.
 
+```
     If you run GRUB, then at the boot menu simply hit `c` to get a console, then
     type `kernel=(hd0,0)/<PATH>/kernel` (substituting appropriate hard
     drive/partition numbers & path, or using `(fd0)` to load a kernel on the
     floppy), then `initrd=(hd0,0)/<PATH>/fs.tar`, and finally `boot`.
+```
 
 4. Assuming the OS has booted, what can you do now?  Well, start by trying `sh`,
 to open another shell.  Then, try `vi gavin.c` to open up the OS source in a