Can't evaluate `CREATE TABLE` with `INDEX` in MySQL

`sqlparser-rs` couldn't evaluate following MySQL statement.

```mysql
CREATE TABLE users (id INT, name VARCHAR(10), INDEX (id));
```

Evaluating this statement by using cli caused following error.

```
[nannany@nannanynoMBP sqlparser-rs (main %=)]$ cargo run --example cli create_table.sql --mysql
Finished dev [unoptimized + debuginfo] target(s) in 0.02s
Running `target/debug/examples/cli create_table.sql --mysql`
Parsing from file 'create_table.sql' using MySqlDialect
2022-04-17T07:36:14.347Z DEBUG [sqlparser::parser] Parsing sql 'CREATE TABLE users (id INT, name VARCHAR(10), INDEX (id));
'...
Error during parsing: ParserError("Expected a data type name, found: (")
```

I tried version 0.16.0.

首先，使用 MySqlDialect 和提供的 create_table.sql 輸入，透過 CLI 範例重現該陳述式。追蹤資料表層級 INDEX 子句的剖析器錯誤，然後為此 MySQL 陳述式新增涵蓋範圍，並驗證它能成功剖析，且不會讓其他 CREATE TABLE 形式發生回歸。

由索引模型根據 Issue 內容生成。