Due to causing content images to be rendered in unexpected ways.
- Also removed CSS filters from other image usage.
- Tweaked header CSS filtering to not be so aggressive.
- Forced WYSIWYG editor to be on its own layer since that would allow
massive larger performance increases in Safari, especially when using
dark mode.
Closes#2045.
Closes#2154.
- Updated editor, and other area, styles to look okay in dark mode.
- Used tinyMCE theme generator to create dark mode theme.
- Updated tinymce to latest 4x version.
