/// This macros provides the fast creating [BTreeMap](std::collections::BTreeMap) object
///
/// # Examples:
/// ```
/// use add_macro::btree_map;
/// use std::collections::BTreeMap;
///
/// assert_eq!(
/// btree_map! {
/// "key1" => "value1",
/// "key2" => "value2",
/// },
/// BTreeMap::from([("key1", "value1"), ("key2", "value2")])
/// );
/// ```