@krunoslav if your intent is to play around with Vue.js or ReactUI framework, you should be trying your hands on the new dashboard framework (Most of it is Cloud native though). Only Splunk Dashboard Beta is available with Enterprise but does not allow extensions.)
@niketnilay Thanks for suggestion, I will look at it, but it's beta and I need something stable. Moreover, I don't think it will help a lot here. So, I'm afraid I still need help with integration of external libraries from Splunk in a Vue project.
Like I said for Cloud Native application you can check out Splunk Cloud Services.
Dashboard Beta will anyways not support extensions!