fix even more broken markdown links

Added `bin/find-missing-links.sh` tool to check for
markdown links to missing local files.

Regarding the missing link tool:

```
    Here be extended regular expression magic dragons! :-)
```

Added `make find_missing_links` to the top level Makefile.

Added `make find_missing_links` to `make www` and `make quick_www`.

Ran `make www` to perform the above.

TODO: Fix markdown links to missing local files.

2014/maffiodo2/README.md

@@ -63,7 +63,7 @@ Who will be the first to tweet this source?  How many re-tweets will such tweet
 get?  And how many people will really understand the tweet?
 
 Judges' 2023 update: Last year we would have referred to a
-[toot](https://en.wikipedia.org/wiki/Mastodon_\(social_network\)#Comparison_to_Twitter),
+[toot](https://en.wikipedia.org/wiki/Mastodon_(social_network)#Comparison_to_Twitter),
 as in a [Mastodon](https://fosstodon.org/@ioccc) *toot*.
 This year we might have mentioned the term
 [publish](https://www.itechpost.com/articles/115087/20221116/mastodon-officially-replaced-toot-publish.htm)