Fix incorrect error when invalid language passed.

[roncli]

this.resources is not defined at the time this error would be thrown, so we use resources which is defined.

Example code that triggers the incorrect error:

const XIVAPI = require(".");
const xiv = new XIVAPI({"language": "invalid"});

Currently, the error is:

Uncaught TypeError: Cannot read properties of undefined (reading 'languages')
    at new XIVAPI (/mnt/s/dev/git/github/roncli.com/node-roncli-com/node_modules/@xivapi/js/XIVAPI.js:31:74)

After this change, the error becomes:

Uncaught Error: Invalid language given, must be one of: en,ja,de,fr,cn,kr
    at new XIVAPI (/mnt/s/dev/git/github/xivapi-js/XIVAPI.js:31:10)