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/birken/README.md

@@ -180,7 +180,7 @@ for [Khan](https://memory-alpha.fandom.com/wiki/Khan_Noonien_Singh) (in the
 final engagement in [Star Trek II: The Wrath of
 Khan](https://memory-alpha.fandom.com/wiki/Star_Trek_II:_The_Wrath_of_Khan), the
 damaged Enterprise managed to disable the USS
-[Reliant](https://memory-alpha.fandom.com/wiki/USS_Reliant_(NCC-1864) ship)'s shield
+[Reliant](https://memory-alpha.fandom.com/wiki/USS_Reliant_(NCC-1864) ship)'s shield
 generator by accessing its prefix code: 16309).