Avoid wiping quickfix list on `:RescriptFormat`

[sinap-fb]

(This probably applies to the :RescriptBuild command as well)

On format, the users quickfix list should not be wiped, since it can be a list of stuff unrelated to Rescript.

Currently, it is getting wiped here:

vim-rescript/autoload/rescript.vim

Line 164 in 08de541

call setqflist([])

I think this should be achievable using quickfix IDs.

Thanks

[ryyppy]

yeah, i made this because I didn't know how to isolate quickfix results to certain scope. Didn't know about ids... currently I don't consider this a very big problem (except for wiping e.g. build errors from quickfix.. but for that I usually just rerun the build real quick with a hotkey).

Don't have much time right now to fix this right away, so I would be open for a PR!