generalize project into a generic list-manager rust macro

[kantord]

The entire project could be largely generalized into a rust macro that can be used to generate simple, synched list managed apps. basically, blogtato is just a simple list managed with a sync feature and a few built in scripts for fetching rss feeds. most of the logic could be entirely reused for other use cases

it could look sth like this:

synctato_app! {
  schema {
    feeds: FeedSource,
    posts: FeedItem,
    reads: ReadMark,
  }
  query {
    main_table: posts,
    group_by: { "/d" => date, "/f" => feed },
    filter_by: { ".read" => ..., ".unread" => ... },
    date_field: published,
    shorthand_field: feed,
  }
}

this way almost everyhing that is not RSS-specific could be removed from this repo