update year level .filelist

Added new YYYY/index.html files.

Removed var.mk as such special top level files are
added (or not) in various bin tools.

2018/.filelist

@@ -6,8 +6,8 @@
 2018/.gitignore
 2018/guidelines.txt
 2018/hint.css
+2018/index.html
 2018/iocccsize.c
 2018/iocccsize.mk
 2018/rules.txt
 2018/.year
-var.mk