Эшкн написан неправильно, либо ты пользуешь async/await либо promise.then.
в твоем случае
async categoryBySlug ({commit}, slug) {
commit(CATEGORY_BY_SLUG)
const response = await axios.get(`${API_BASE}/categories`, {
params: {
slug: slug
}
})
commit(CATEGORY_BY_SLUG_SUCCESS, response.data.data)
},
async allProductsById ({commit}, id) {
commit(ALL_PRODUCTS_BY_ID);
const response = await axios.get(`${API_BASE}/products`, {
params: {
category_id: id
}
})
commit(ALL_PRODUCTS_BY_ID_SUCCESS, response.data.data)
},
