Redaction Truncate

Truncates token values to 4 chars plus ....

var redactor = logly.Redactor.init(allocator);
defer redactor.deinit();

redactor.config.truncateLength = 4;
redactor.config.truncateSuffix = "...";
try redactor.addField("token", .truncate);

const redacted = try redactor.redactField("token", "abcdef");
defer allocator.free(redacted);
// redacted == "abcd..."

Output:

Truncated: supersec...
Hashed: [HASH:d5b9ce540d31f2d3]