Character '-' not accepted in JSON key
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### Summary

Using a mutation to add data to my database. One of the field is a JSON structure. If within that JSON structure, a key contains '-' (e.g., "user-state"), postgraphile reports `Syntax Error: Invalid number, expected digit but got: \"s\"`

If I replace with "user_state" in the example, then everything works. Unfortunately, for legacy purposes, the source of this data cannot be modified.

### Steps to reproduce

An example input:
```json
{ "query": "mutation {
  addEvent(input: {
    clientMutationId: \"AddEvent\",
    user: \"1234\",
    ip: \"127.0.1.1\",
   log: {version: 1, agent: \"monitor\", host: \"localhost\", type: \"system\", timestamp: \"1632406094\", event: {user-state: \"idle\"} }
}) {
 clientMutationId
}

}"
}
```

### Expected results
I've looked at various answers online as well as json.org. As far as I know, '-' is a valid character in a JSON key.

### Actual results

```json
{
  "errors": [
    {
      "message": "Syntax Error: Invalid number, expected digit but got: \"s\".",
      "locations": [
        {
          "line": 1,
          "column": 206
        }
      ],
      "stack": "GraphQLError: Syntax Error: Invalid number, expected digit but got: \"s\".\n    at syntaxError (/node_modules/graphql/error/syntaxError.js:15:10)\n    at readDigits (/node_modules/graphql/language/lexer.js:426:38)\n    at readNumber (/node_modules/graphql/language/lexer.js:373:16)\n    at readToken (/node_modules/graphql/language/lexer.js:259:14)\n    at Object.lookahead (/node_modules/graphql/language/lexer.js:54:43)\n    at Object.advanceLexer [as advance] (/node_modules/graphql/language/lexer.js:44:33)\n    at Parser.expectToken (/node_modules/graphql/language/parser.js:1399:19)\n    at Parser.parseName (/node_modules/graphql/language/parser.js:94:22)\n    at Parser.parseObjectField (/node_modules/graphql/language/parser.js:579:21)\n    at Parser.item (/node_modules/graphql/language/parser.js:563:21)"
    }
  ]
}
```


### Additional context

postgraphile v4.12.3

