`use_course()` should open projects in Positron without an `.Rproj` file

[cwickham]

use_course() relies on the presence of an .Rproj file to trigger opening the project via rstudioapi::openProject():

usethis/R/course.R

Lines 398 to 409 in 4aa55e7

	if (is_interactive()) {
	rproj_path <- rproj_paths(target)
	if (length(rproj_path) == 1 && rstudioapi::hasFun("openProject")) {
	ui_bullets(c("v" = "Opening project in RStudio."))
	rstudioapi::openProject(target, newSession = TRUE)
	} else if (!in_rstudio_server()) {
	ui_bullets(c(
	"v" = "Opening {.path {pth(target, base_path)}} in the file manager."
	))
	utils::browseURL(path_real(target))
	}
	}

For a project designed to be used in Positron, this file may not be present, but it would be nice if the project still opened in a new Positron window.

[jennybc]

usethis should probably be marking any packages/projects that it helps to create with .here if it looks like that might be the only indicator of project-hood. That would clearly apply to create_project() and basically applies to use_course() as well. I think marking it with .here might be preferable to "just" opening it the first time, because it sets people up for greater success going forward.

Update/correction: create_project() has been writing .here for a long time, if it's not going to write an .Rproj file. So I'm just going to add similar behaviour to use_course().