Web: Only load data if it is not present in local storage + window alert bug about epfl-interactive-coursebook

[valentinoli]

It turned out that we were calling the api.js in CourseViz.vue where the data was not sure to have been loaded into local storage. So I changed the place where the data is loaded into local storage to the root component App.vues beforeCreated lifecycle hook, which makes more sense:

  async beforeCreate() {
    try {
      // Load all data to local storage
      // if it hasn't been loaded already
      await api.loadAllData();
    } catch (err) {
      console.error(err);
      this.error = err;
    } finally {
      this.loading = false;
    }
  }

As a consequence the displaying of the skeleton loader is now the root component's responsibility. And the skeleton loader is only displayed if the data is not present in the user's browser. Another upside about this is that the data is loaded regardless of which view the user opens first, and not only the index view.