OS Features - Extension Edition szerző: Lastie

Adds new features and themes to Online Sequencer!

Sequencer features include:
- AdBlock
- MultiSolo (pending removal from because of new Online Sequencer update adding this)
- Slider Text Inputs
- And a BPM tapper.

Chat features:
- Midnight Rose theme
- Image auto hider
- Chat user blocker
- Chat name stylizer (i need to fix, as i accidentally broke it in the port to firefox)
- And link embeds

Themes:
- Midnight rose chat theme
- And a WIP site-wide midnight rose theme.

Also adds a small fix to the forums page allowing the chat popup to work.