Add GraphQL schema

[s1na]

The schema can be explored via https://s1na.github.io/graphql-schema-explorer/?url=https://raw.githubusercontent.com/s1na/execution-apis/7b57bc60a59dc5ac8d8bffc0e5df4a12134cf2ae/graphql.json

This was exported from geth which has some EIP-1559 related fields in addition to the eip.

Fixes #163

This is the script I used to generate this against a live node:

const { buildClientSchema, printSchema, getIntrospectionQuery } = require('graphql')
const { request } = require('graphql-request')

const endpoint = 'http://localhost:8545/graphql'

async function main() {
    const q = getIntrospectionQuery()
    const res = await request(endpoint, q)
    const types = []
    console.log(JSON.stringify(res, null, 2))
}

main().then().catch((err) => console.log(err))

[lightclient]

This is really neat - thanks for this. Do you mind also doing the following:

1. Add the script you provided into the scripts directory here + adapt it to actually write the schema to the graphql.json file?
2. Add a CI check to validate the schema (maybe something like this)?

[s1na]

Done. Re 2. I use the semantic validation offered by the graphql library itself, but it doesn't check other lint-ish rules like the one you linked. Happy to add that too if you think it helps

[lightclient]

Thank you! The validator you wrote seems fine. The main thing I want to avoid is having a graphql.json file that can't be consumed for some reason, so it seems like buildClientSchema will catch that.