Added 'sqlite' key to db.BuilderFuncMap for noncgo sqlite driver support

[ganigeorgiev]

The noncgo sqlite driver (https://pkg.go.dev/modernc.org/sqlite) uses sqlite as driver key.
This PR adds the key to the db.BuilderFuncMap, so that users don't have to do:

func init() {
    dbx.BuilderFuncMap["sqlite"] = dbx.BuilderFuncMap["sqlite3"]
}