add YYYY/.filelist files

A _YYYY/.filelist_ is a simple list of files for a given IOCCC year
that need to be present when building a _YYYY_ level compressed
tarball.  The list is relative to _docroot_ (top level repo directory).

We do not need a complex JSON file for such a simple list of files.
We only care about checking for the existence of files when forming
_YYYY_ level compressed tarball.

1989/.filelist

@@ -0,0 +1,7 @@
+1989/1989.tar.bz2
+1989/Makefile
+1989/README.md
+1989/.filelist
+1989/rules.txt
+1989/.year
+var.mk