Implement knex-related resources

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: 'hi@example.com' }) {
firstName
lastName
}
}
}
```

Start with src/askscript/__tests__/02-query/query-09-node_with_expression.ask and read how the mocked knex and where usage is represented. Trace how AskScript exposes query resources, then determine the supported knex methods and verify that the sample query returns friends with firstName and lastName.

Written by the indexing model from the issue text.