Going to generate a series of small PRs. Better for you learning JS and me learning your application.
added actions, functions, and constants files as placeholders
introducing ES6 classes in models.js (also a common directory to hold shared files)
moved mutations out of store.js (eventually shifting to Vuex modules)
no reason as far as I can tell for a pseudo random character id, let store keep track of an incremented id and assign the next available to any new character, no collision possible, plus you can order your characters through the logical clock that is their id property if necessary
Going to generate a series of small PRs. Better for you learning JS and me learning your application.