relates to #1168

This addresses a few problems with reaction colors:

- The state-checking conditionals for reaction text, background, and border
  were inconsistent, making it difficult to choose colors for each state
  (normal, hovered, and self reactions) that worked well in all themes.
- The QPalette::Highlight color was being misused as a text/foreground color.
  This color role is intended for background areas.  It has little contrast
  against the background in themes like KDE Plasma's Breeze High Contrast,
  so using it for text and icons makes those things difficult to read.
  https://doc.qt.io/qt-5/qpalette.html#ColorRole-enum
- The reaction border was drawn in the same color as normal text, making it
  so bright in some dark themes that it distracted from reading nearby text.

Fixes Nheko-Reborn/nheko#1159

This helps with #1065, although I think making sure the message input box gets focus by default would be worthwhile.

see #1042
see #483

Requires MSC3266

Fixes #1129

fixes #1114

fixes #919

fixes #917

* Added escape handler for uploads

* Update MessageView.qml

Changed if-else conditions to handle only one escape at a time

fixes #1088