feat: add support for variables in subgraphRequest function

[wa0x6e]

This PR adds support for variable when sending graphql request via the subgraphRequest utils function.

Injecting variables via the options argument is very ugly, but in order to be backward compatible, this seems to be the only way.

How to test

import { VariableType } from 'json-to-graphql-query';

const result = await subgraphRequest(
    'https://hub.snapshot.org/graphql',
    {
      __variables: {
        id: 'String!'
      },
      space: {
        __args: {
          id: new VariableType('id')
        },
        id: true,
        name: true
      }
    },
    {
      variables: {
        id: 'aave.eth'
      }
    }
  );
  console.log(result);

It should print

{ space: { id: 'aave.eth', name: 'Aave' } }

[ChaituVR]

Where do we want to use this?

[wa0x6e]

In sequencer, in the delegate statement pr. Some graphql api does not work with the hardcoded variables inside the query, since they don't use string type, but enum

[ChaituVR]

tAck