Loads cached subjects data from local storage. If cache doesn't exist or reload is TRUE, fetches fresh data from the API and saves it to cache.
Examples
if (FALSE) { # \dontrun{
# Load cached data (or fetch if no cache exists)
subjects <- wk_load_subjects_cache()
# Force reload from API
subjects <- wk_load_subjects_cache(reload = TRUE)
# Load specific levels only
subjects <- wk_load_subjects_cache(levels = 1:5)
# Load specific types only
subjects <- wk_load_subjects_cache(types = "kanji")
} # }