Update diagrams to have the same visual style

[NataliaTepluhina]

Currently, we have a few diagrams that should be updated:

• Lifecycle Hooks diagram - we need to rename lifecycle hooks (beforeDestroy -> beforeUnmount, destroyed -> unmounted
• Scoped slots diagram - it's just ugly and that's on me 😓

It would be also nice to have diagrams sharing the same visual style

[phanan]

I can handle this.

[phanan]

Couple of changes as discussed in Discord:

• No new Vue() anymore => replace with app = Vue.createApp(options); app.mount(el)
• No el option anymore => delete the whole "has el option?" branch
• vm.$destroy is now app.unmount() => modify the diagram accordingly
• destroyed is now unmounted => modify the diagram accordingly