improve news.html and mastodon info

Added "2024-04-20" news update.

Fixed format for "2023-05-22" news.

Fixed bad links to `judges.html`.

Add "Jump to: top" near the bottom.

The `make gen_top_html` no longer builds `next/rules.html`
nor `next/guidelines.html`.  This is being done by
the `bin/gen-status.sh` tool and `make gen_status`.

Moved `make gen_top_html` after `make gen_status` in the top level
Makefile rules for `make www` and `make quick_www` because
`bin/gen-status.sh` uses the modification date of `news.html` (that
make gen_top_html might modify) when forming `status.json`.

Added FAQ 6.12 for "What is Mastodon and why does IOCCC use it?".

Simplified `contact.html` mastodon info to refer the above FAQ
for further mastodon information.

Changed `bin/gen-top-html.sh` VERSION from "1.4.2 2024-04-21"
to "1.4.3 2024-04-21".

The `bin/gen-status.sh` tool will build `next/rules.html` and/or
`next/guidelines.html` if they are missing or empty.

Changed `bin/gen-status.sh` VERSION from "1.3 2024-04-14"
to "1.4 2024-04-21".

Run `make gen_top_html gen_status` to perform the above.

status.json

@@ -2,6 +2,6 @@
     "no_comment" : "mandatory comment: because comments were removed from the original JSON spec",
     "IOCCC_status_version" : "1.0 2024-03-09",
     "contest_status" : "closed",
-    "news_update" : "2024-04-18T22:49:50+00:00",
+    "news_update" : "2024-04-21T22:08:12+00:00",
     "status_update" : "2024-03-31T05:02:06+00:00"
 }