Support stringifying non-exhaustive enum to json

[pfgithub]

test "stringify non-exhaustive enum" {
    const E = enum(u8) {
        foo = 0,
        _,
    };
    try testStringify("\"foo\"", E.foo, .{});
    try testStringify("1", @as(E, @enumFromInt(1)), .{});
}

It stringifies the named ones to strings and unnamed ones to a number, which parses just fine into an enum already.

I'm not sure if there's a better way to detect if the active field is unnamed - if doesn't support both _ and else, and tagName doesn't return an optional for non-exhaustive enums.

[thejoshwolfe]

great idea! and thanks for the test! just missing documentation. The other suggestion is optional.

[pfgithub]

Added to the documentation comment, switched to recurse instead of writing raw text, and updated for the lowercase std.builtin.Type change

[thejoshwolfe]

thanks!