Add contract pre population

[darrenvechain]

This PR allows devs to pre-load contracts into inspector to speed up local development. Create a contracts.json and mount its directory to /usr/share/nginx/html/abis

Eg:

services:
  inspector:
    build:
      context: .
    environment:
      NODE_ENV: production
      VUE_APP_SOLO_URL: http://localhost:8669
    volumes:
      # This allows us to pre-populate the contracts. Your local path should contain a file called `contracts.json`
      - "./examples/abis:/usr/share/nginx/html/abis"
    ports:
      - 8083:80