Added functionality to fade out a show when a new show starts.

[btelliot]

OB Description

1. Updated README.md with some of my notes from learning the modules.
2. Added a fade out to the main-volume mixer to make the transition between shows seamless.
3. Updated the HTTP admin to modify or disable the fade.
4. Tested by creating hundreds of 5-minute long shows with a single dynamic playlist, which allowed me to hear the fade go off roughly every 5 minutes. Tested modifying the length, and I found that 10 seconds sounds very good. My setting was all containerized, so I was listening via VLC connected to an Icecast stream.
5. The way OBPlayer cuts off shows abruptly had been driving me CRAZY for +5 years, so it's nice to have a fix!

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Testing Environments

OpenBroadcaster Component and Version

• OBServer
• OBPlayer
• Module
• Other

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code and corrected any misspellings
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Thanks for contributing!