Add an option to reverse activity feed entries

[rachids]

I added an option in Parameters > Appearance that allow to reverse the order of activities so that new activity will be added at the bottom, just like chat.

[Durss]

Nice first shot but it's not yet good enough in terms of UX to be acceptable. For now only the items order is reversed but there should also be an auto-scrolldown, otherwise new items won't be visible to the streamer until s·he manually scrolls down.

Also the auto-scrolldown should ideally not conflict with any user interaction. If we scroll up the list it shouldn't go down automatically when a new item is added to the list. A naive way to do that is to only auto-scroll down if the list is already at the bottom when a new item is added.

As a fine tunning if the list could scroll smoothly like the chat it would be perfect. But this is very tricky to implement so it's just bonus.

[rachids]

• [ ] Make the animations work when the option is not reverse
• [ ] Scroll auto after a given delay
• [ ] Block auto-scroll if user is scrolling