Read a Settings Line

A settings file has lines like volume = 7. Each line has a key, an =, and a value.

Task: write parse_setting(line) that returns a list [key, value].

• Split at the first = only. The value can contain more = signs, and they stay in the value.
• Remove whitespace from both ends of the key and of the value.
• If the line has no = at all, return [the whole line trimmed, ""].