using `roc_cache_packages_dir()` instead, which will return "~/.cache/roc/packages", which was the existing functionality, but `roc_cache_dir()` will now return "~/.cache/roc"
Implements the new app header syntax as discussed in Zulip [1].
app [main] {
cli: platform "../platform/main.roc",
json: "../json/main.roc"
}
Old headers still parse and are automatically upgraded to the new
syntax by the formatter.
[1] 418444862