[feature request] add new “success” symbol

[DerekNonGeneric]

After stumbling upon the log-symbols package, I realized that we should probably also include a symbol for “success”, which seems to be a reasonably common log symbol. This symbol should also have a fallback for Windows CMD, which only supports a limited character set (non-Unicode). This is somewhat related to #59, which would add fallbacks for the Unicode symbols we already offer.