Add missing package descriptions for GoDoc

database/doc.go

http/client/doc.go

http/cookie/doc.go

http/request/doc.go

http/route/doc.go

integration/instapaper/doc.go

integration/nunuxkeeper/doc.go

integration/pinboard/doc.go

integration/pocket/doc.go

integration/wallabag/doc.go

reader/atom/doc.go

reader/date/doc.go

reader/encoding/doc.go

reader/feed/doc.go

reader/icon/doc.go

reader/json/doc.go

reader/opml/doc.go

reader/processor/doc.go

reader/rdf/doc.go

reader/readability/doc.go