Unicode based programming language

As you can see from other answers, most modern languages allow this, including Perl, Python, Go, Ruby, Java, C♯, variants of lisp, Fortess, ADA, and many more. C and C++ do not, but those aren’t modern.

Regarding C♯, from MSDN:

The rules for identifiers given in this section correspond exactly to those recommended by the Unicode Standard Annex 15

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As for converting an API to a chosen language - this is not feasible. You would require a translator that understands the nuances and meaning of every method, variable and class name and translate those correctly - this is not the same as being able to use the characters of a chosen language in code.

Ada (among others) allows for internationalized identifiers using UNICODE.

However, my personal opinion is software should be written using a single, universally understandable and sufficiently simple language (English, obviously) to encourage collaboration, ensure understandability and reusability of code.

Delphi has that feature since Version 2009

Javascript has this feature.