Add loader

[kjugi]

Add loader when clicking on the button or when loading/updating some data.

• When changing step
• When loading i.e methods

[kjugi]

Must think about the new method of calling loader. Don't want to manually change this.$store.state.loader each time. Must think about maybe some eventListener on specific elements and toggle this action or sth 🤔

[kjugi]

And think about storing styles. For now, in the BaseLoader component, I have <style> tag.

[szafran89]

Good approach it would be to write mutation setLoading (state, payload) and commit it commit('setLoading', true|false) when you make async requests inside store actions.

[kjugi]

As I wrote in my first PR to loader in buttons:
If we want to add loader on start than must deal with v-cloak and add some styles to loader