Adding a string and a promise of string give different results.

[dduponchel]

When I add a string without the binary option, it is treated as an unicode string.

zip.file("txt", "é");
zip.file("txt").async("text").then((txt) => console.log(txt));
> é

When I add a promise of string without the binary option, it is treated as a binary string.

zip.file("txt", Promise.resolve("é"));
zip.file("txt").async("text").then((txt) => console.log(txt));
> �

Expected: same behavior between the two use cases.

Note to self: also fix the documentation of binary which is quite confusing.