Add custom query option.

[CarterSmarty]

No description provided.

[EmeraldPandaTurtle]

Looks pretty good

Some bad practices that should be avoided though

if !self.options.custom_queries.is_none() {
    for (key, value) in self.options.custom_queries.clone().unwrap() {
        builder = builder.query(&[(key, value)]);
    }
}

Should instead follow pattern matching so it should be

if let Some(queries) = self.options.custom_queries.cloned() {
    for (key, value) in queries {
        builder = builder.query(&[(key, value)]);
    }
}

We should probably rethink the name for with_custom_comma_separated_query to instead be something like with_appended_query_item, and change the doc comment to better describe the result. It's just a little vague.

Otherwise looks good to me.