🎁 🐜 Support all available versions of @vue/composition-api

This update brings greater compatibility with past and future versions of the @vue/composition-api plugin for Vue 2. Thanks to a well-thought-out PR by @phatj and input from @J3m5, feathers-vuex now supports all version fo the composition-api plugin. In version 0.6.7 of the plugin, the createElement export was renamed to h to match the exports in Vue 3. Even though it was a breaking change for the composition api plugin, @phatj was able to produce code that works for all versions without a breaking change for feathers-vuex! 🎉