Add placeholder `:1` and `$1`

[Evgenii Yaroshenko]

This placholder ? working but :1 and $1 not work.

Example

let sql = "DELETE FROM users WHERE user = $1 AND password = $2";
    let res = parse_query(sql);
    assert!(res.is_ok());
// or
 let sql = "DELETE FROM users WHERE user = :1 AND password = :2";
    let res = parse_query(sql);
    assert!(res.is_ok());

Result:

Err(
    "failed to parse query"
)