read_vpts(): support reading remote files

[peterdesmet]

read_vpts() only supports reading local files, not files from URL:

> read_vpts("https://opendata.meteo.be/ftp/observations/radar/vbird/bewid/2020/bewid_vpts_20201014.txt")
Error in read_vpts("https://opendata.meteo.be/ftp/observations/radar/vbird/bewid/2020/bewid_vpts_20201014.txt") : 
  File https://opendata.meteo.be/ftp/observations/radar/vbird/bewid/2020/bewid_vpts_20201014.txt doesn't exist.

This is caused by the file.exists() check in the function, which returns FALSE for URLs:

bioRad/R/read_vpts.R

Lines 26 to 28 in 33ec6ed

	if (!file.exists(file)) {
	stop(paste("File", file, "doesn't exist."))
	}

How could this check be adapted to support reading remote files from URL?

[bart1]

Sometimes it it worth to make things work based on connections, it also allow to work easily with compressed files which I guess is worth for the vpts txt files