Display brightness support (#26)

* cleanup

* brightness control and app

* cleanup

* persistant storage of display settings

* fix for missing include

* header cleanup

* fix pc build

* add docs

* move display app to tactility project

docs/ideas.md

@@ -7,10 +7,22 @@
 is not automatically called. This is normally done by a hook in `FreeRTOSConfig.h`
 but that seems to not work with ESP32. I should investigate task cleanup hooks further.
 - Set DPI in sdkconfig for Waveshare display
+- Try to drive Yellow Board backlight with PWM to reduce backlight strength
+- Show a warning screen if firmware encryption or secure boot are off when saving WiFi credentials.
+- Show a warning screen when a user plugs in the SD card on a device that only supports mounting at boot.
+- Try out Waveshare S3 120MHz mode for PSRAM (see "enabling 120M PSRAM is necessary" in [docs](https://www.waveshare.com/wiki/ESP32-S3-Touch-LCD-4.3#Other_Notes))
+- Fix for dark theme: the wifi icons should use the colour of the theme (they remain black when dark theme is set)
  
 # Core Ideas
 - Make a HAL? It would mainly be there to support PC development. It's a lot of effort for supporting what's effectively a dev-only feature.
 - Support for displays with different DPI. Consider the layer-based system like on Android.
+- Display orientation support for Display app
+- If present, use LED to show boot status
+
+# App Improvement Ideas
+- Make a Settings app to show all the apps that have a "settings" app type (and hide those in desktop)
+- Sort desktop apps by name.
+- Light/dark mode selection in Display settings app.
 
 # App Ideas
 - Chip 8 emulator