Show actual character instead of escaped code point notation (`\u****`) in string literals

[TonalidadeHidrica]

As a Japanese user I common encounter with JSON files with a plethora of "\u65e5\u672c\u8a9e" which are hexadecimal escape sequences of Unicode code points. It would be nice if jless automatically parses them to show the actual string that they refer to.

[JubilantJerry]

I've encountered this same issue, and implemented this feature in a fork: https://github.com/JubilantJerry/jless_unicode But I'm not much of a Rust programmer so my implementation is probably a kludge. I only tested the bare minimum functionality. I agree that the main repo could consider adding this feature.