Major JUCE features and updates

This file lists the more notable headline features. For more detailed info
about changes and bugfixes please see the git log and BREAKING_CHANGES.md.

Version 9.0.4

• Added a MIDI device disconnection listener API
• Fixed multiple Windows MIDI device disconnection issues
• Fixed several MessageManagerLock issues
• Fixed Windows window placement when the display scale changes
• Fixed multiple Linux windowing and system tray issues
• Fixed some LV2 hosting issues
• Fixed XmlElement whitespace handling
• Added a NEEDS_OPENGL_ES CMake option for Linux
• Added protection against malformed String input