process_all_messages_files does not check that given files are messages files before reading #30
Description
I had a .zip file temporarily in one of the directories that a project was scanning for messages files to perform an export. When calling IntlMessagesDatabase#processAllMessagesFiles, that file was included because of a broad glob pattern (and the expectation that only valid files would be present), and the crate panicked at public::process_all_messages_files saying the file couldn't be read because it did not contain valid UTF-8.
Ideally, the database should check that the file is actually a messages file before trying to read it (based on file name), or should at least provide a more accurate, catchable error to describe why the processing failed. In this case, it would've been fine to just skip the file rather than panicking, for example.