move fix thanks a file, update top level html links, rename CONTRIBUTING.md

The fix thank you's have been moved from `README.md` to
`thanks-for-fixes.md`.

**WARNING**: Some mistakes may have been made in doing this.
We presume later changes by others will correct any issues.

The `CONTRIBUTING.md` was renamed `how-to-enter.md`.

A 3rd line of links was added to top level html such as
`contact.html`, `index.html`, `judges.html`, `winners.html`,
and `years.html`.

Improved blank line use in a number (but not all) `README.md` files.

2004/gavin/README.md

@@ -10,12 +10,14 @@ UK
 make
 ```
 
+
 ## To run:
 
 ```sh
 ./gavin
 ```
 
+
 ## Try:
 
 To enjoy the results (on a Linux/x86 machine):
@@ -62,18 +64,6 @@ vi README.md
 
 Press and hold any key.
 
-### Alternate method:
-
-[Yusuke Endoh](/winners.html#Yusuke_Endoh)  provided the `kernel` and `fs.tar`
-files which can be used if you cannot normally use this entry. Instead of
-generating the files just use the files provided, found under the [img/](img/)
-directory. Note that the `img/fs.tar` extracts into `fs/` so you will have to
-fix the tarball; this is done this way to prevent extraction from the entry
-directory overwriting the files and causing `make clobber` to wipe some of them
-out.
-
-Thank you Yusuke!
-
 
 ## Judges' remarks:
 
@@ -103,6 +93,7 @@ What you can do and what you cannot do in such programs?
 The program called `prim`, written by the judges, computes and prints prime
 numbers.
 
+
 ## Author's remarks:
 
 This is a 32-bit multitasking operating system for x86 computers,
@@ -174,6 +165,7 @@ at which a Linux bootloader loads an x86 kernel image).
 
 \* ;-)
 
+
 ## Copyright and CC BY-SA 4.0 License:
 
 This file is Copyright (c) 2023 by Landon Curt Noll.  All Rights Reserved.