Non-Printable Character Detection

Replace non-printable characters, e.g., zero-width spaces, with a visible symbol.

Replace non-printable characters, e.g., zero-width spaces, with a visible symbol ❖ (U+2756).

Only formatting characters (\p{Cf}) ^1 are included.

Its detection range is much wider than the Firefox addon ZeroWidth Detection ^2, as the addon only tests four specific characters ^3.

I didn't find a Chrome counterpart.