Exercise: describe a value

Write a function func describe(v any) string that describes a value by its type. For an int it returns "int " followed by the number, and for a bool it returns "bool " followed by true or false. For a string the result is "string of N bytes", where N is the length of the string in bytes.

• describe(42) → "int 42"
• describe("мир") → "string of 6 bytes"
• describe(3.5) → "unknown"

Constraints: the string may be empty, and then N is 0; for nil the function returns "nil", and for any other type, such as float64, it returns "unknown".

Do not add extra imports unless the task says so explicitly.