Have redbean show zip listing as default / handler

If an "index.lua" or "index.html" doesn't exist in zip file or the
filesystem, and no redirects have been defined for it either, then
redbean will render a listing of the zip central directory content
only if the request uri points to the root path.

tool/net/.init.lua

@@ -1 +1,2 @@
 -- special script called by main redbean process at startup
+ProgramRedirect(0, '/favicon.ico', '/tool/net/redbean.ico')