add toggle for alphabetical sort of language list in /code

Description

only one html/css change requred, reference implementation:
https://codepen.io/dym-sh/pen/gORLrGQ?editors=1100

• also add Dart as alias for Flutter
• also set column-count to auto, no need for screen-size-breakpoints dependency

Motivation

so, in https://graphql.org/code/
i was scanning the list for Dart, but only found Flutter after i started going one-by-one
both of which would be way faster if list would be in alphabetical order and had Dart

Collaboration

sure.. not sure if its something important enough, so just an issue atm, i can prob send PR within a week

[Urigo]

that's a good idea, we would love to accept a PR for that change