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\'")`

Start by reproducing the reported query and error with the PostgreSQL dialect, then inspect how is_identifier_start and is_identifier_part handle the JSON extraction operator and prepared-query placeholders. Done means the query parses successfully without requiring ad hoc identifier characters, with coverage for the shown SQL expression.

Written by the indexing model from the issue text.