Improve confusing error messages for JS client

[Migweld]

Is your feature request related to a problem? Please describe. Syntax errors within GROQ queries throw a 'Must be an attribute or string key' error. The stacktrace doesn't give a great deal of information as to where the problem is. Example below:

Very simple mistake to make. Missing comma after 'slug':

`
    {
      "work": *[_type == "caseStudies"]{
        title,
        slug
        tags,
      }
    }
  `

Error message given:

Must be an attribute or a string keyClientError: Must be an attribute or a string key
    at onResponse (/Users/craig/Documents/projects/flo-site-v5/node_modules/@sanity/client/lib/http/request.js:27:13)
    at /Users/craig/Documents/projects/flo-site-v5/node_modules/get-it/lib-node/util/middlewareReducer.js:10:22
    at Array.reduce (<anonymous>)
    at applyMiddleware (/Users/craig/Documents/projects/flo-site-v5/node_modules/get-it/lib-node/util/middlewareReducer.js:9:29)
    at onResponse (/Users/craig/Documents/projects/flo-site-v5/node_modules/get-it/lib-node/index.js:81:22)
    at /Users/craig/Documents/projects/flo-site-v5/node_modules/get-it/lib-node/index.js:48:55
    at callback (/Users/craig/Documents/projects/flo-site-v5/node_modules/get-it/lib-node/request/node-request.js:57:46)
    at /Users/craig/Documents/projects/flo-site-v5/node_modules/get-it/lib-node/request/node-request.js:141:14
    at DestroyableTransform.<anonymous> (/Users/craig/Documents/projects/flo-site-v5/node_modules/simple-concat/index.js:7:13)
    at Object.onceWrapper (events.js:312:28)
    at DestroyableTransform.emit (events.js:228:7)
    at endReadableNT (/Users/craig/Documents/projects/flo-site-v5/node_modules/readable-stream/lib/_stream_readable.js:1010:12)
    at processTicksAndRejections (internal/process/task_queues.js:81:21)

Describe the solution you'd like Relevant error messages, perhaps as a result of validation of the GROQ query itself.

[vicmeow]

Thanks for reporting! More useful messaging would definitely benefit us all!