[graphiql] #3310 broke the schema demo

[acao]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

the schema-demo function on netlify fails with a 500 error and no response or logs on netlify functions

Expected Behavior

schema demo introspection requests and graphql ops should suceed

Steps To Reproduce

1. https://graphiql-test.netlify.app
2. observe failing schema

Module pattern

• graphiql-umd
• graphiql-esm
• graphiql-commonjs

Environment

- GraphiQL Version:
- OS:
- Browser:
- Bundler:
- `react` Version:
- `graphql` Version:

Anything else?

No response

[acao]

should probably just drop express entirely

also, this bug form is a bit wonky. should have rich input for steps to reproduce at least

[acao]

to note, the upgrade with express-graphql is still working fine for e2e tests, but the serverless wrapper for express seems to not be compatible with it, and throws a mystery 500 error

In this PR, I'm adding a netlify handler to our sister repo so that we can implement this without the antiquated express compat layer
graphql/graphql-http#96