Add duckplyr

[Tmonster]

This PR is a WIP PR to add duckplyr.

Things that need to be worked out,

group by queries:
Q8: Query = ans<-x %>% select(id6, largest2_v3=v3) %>% filter(!is.na(largest2_v3)) %>% arrange(desc(largest2_v3)) %>% filter(.by = id6, row_number() <= 2L)))

A fallback situation just occurred. The following information would have been recorded:
  {"version":"0.4.1","message":"Can't use relational with grouped operation.","name":"filter","x":{"...1":"integer","...2":"numeric"},"args":{"dots":{"1":"row_number() <=
  2L"},"by":"...1","preserve":false}}

Q9: tidyverse/duckplyr#265

Join queries:
Q5: Something strange happens where the process seems to get killed the second time it tries to execute it. I may post an issue on the tidyverse duckplyr GitHub if I can find a simple reproducible example.

CC @krlrmlr