Add query example with string in argument

[jamie-reece]

It would be useful to provide an example of how to pass strings to the query argument, not just integers. The following, for example, does not work:

{ "query": "query { works (productSearch: {publicationDateGt: '2021-08-31'}) { title } }" }

I have change single to double quotes etc. and can't seem to get this to work with strings, only integers.