Misleading exception type in DiscordEmbedBuilder

Created by: jammy-dodgers

In the Embed builder, the AddField method can throw an ArgumentNullException for non-null but invalid arguments.

public DiscordEmbedBuilder AddField(string name, string value, bool inline = false)
{
    if (string.IsNullOrWhiteSpace(name))
        throw new ArgumentNullException(nameof(name));
    if (string.IsNullOrWhiteSpace(value))
        throw new ArgumentNullException(nameof(value));
...
}

It would be more accurate to instead throw an ArgumentException when the value is invalid but non-null.

public DiscordEmbedBuilder AddField(string name, string value, bool inline = false)
{
    if (name == null)
        throw new ArgumentNullException(nameof(name));
    if (value == null)
        throw new ArgumentNullException(nameof(value));
    if (string.IsNullOrWhiteSpace(name))
        throw new ArgumentException($"{nameof(name)} cannot be whitespace.");
    if (string.IsNullOrWhiteSpace(value))
        throw new ArgumentException($"{nameof(value)} cannot be whitespace.");
...
}