Implement knex-related resources

[czerwinskilukasz1]

We were talking that it would be nice to have knex methods available in AskScript. A sample file using mocked knex and where can be found here: src/askscript/tests/02-query/query-09-node_with_expression.ask

ask {
  query {
    friends::knex:where({ email: '[email protected]' }) {
      firstName
      lastName
    }
  }
}