Add Support for Postgres JSON prepared query

I am using sqlparser 0.4.0 with rust version 1.36.0
Query:
`
SELECT "emp"."id", "emp"."data" FROM "emp" WHERE id = $1 AND data->>'id'=$2 -- binds: ["emp_name", "123"]
`

Error:
`ParserError("Expected an expression, found: >")`

Dialect Used:
```rust
impl Dialect for MyPostgresSqlDialect {
fn is_identifier_start(&self, ch: char) -> bool {
(ch >= 'a' && ch <= 'z')
|| (ch >= 'A' && ch <= 'Z')
|| (ch == '@')
|| ch == '$'
|| ch == '_'
}

fn is_identifier_part(&self, ch: char) -> bool {
(ch >= 'a' && ch <= 'z')
|| (ch >= 'A' && ch <= 'Z')
|| (ch >= '0' && ch <= '9')
|| (ch == '@')
|| ch == '$'
|| ch == '_'
}
}
```

Even I am adding chars `-` and `>` into `is_identifier_part` then it is giving Error:: `ParserError("Expected end of statement, found: \'id\'")`

先使用 PostgreSQL 方言重現所回報的查詢與錯誤，接著檢查 is_identifier_start 和 is_identifier_part 如何處理 JSON 擷取運算子與預備查詢的預留位置。完成的條件是查詢能成功剖析，不需要臨時加入識別碼字元，且涵蓋所示的 SQL 運算式。

由索引模型根據 Issue 內容生成。