Project restructuring: add tactility-headless (#55)

- Created `tactility-headless` to support ESP32 firmwares that don't require graphics
- `tactility` subproject now contains both PC and ESP32 code (to avoid having to split up `tactility` and `tactility-headless` into separate projects, which would result in a very complex dependency tree)
- `tactility` subproject is now defined as component for ESP32 and as regular module for PC
- Improvements for dispatcher
- Added `project-structure.puml` to docs
- `Gui` service now depends on `Loader` service instead of the reverse
- Added `statusbar_updater` service for updating Wi-Fi and SD card icons

docs/ideas.md

@@ -14,7 +14,7 @@
 - App lifecycle docs mention on_create/on_destroy but app lifecycle is on_start/on_stop
 - Explore LVGL9's FreeRTOS functionality
 - Explore LVGL9's ILI93414 driver for 2.4" Yellow Board
- 
+
 # 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.
@@ -22,7 +22,7 @@
 - 2 wire speaker support
 - tt_app_start() and similar functions as proxies for Loader app start/stop/etc.
 - tt_app_set_result() for apps that need to return data to other apps (e.g. file selection)
-- Introduce co-routines for calling wifi/lvgl/etc functionality.
+- Wi-Fi using dispatcher to dispatch its main functionality to the dedicated Wi-Fi CPU core (to avoid main loop hack)
 
 # App Improvement Ideas
 - Sort desktop apps by name.
@@ -30,7 +30,6 @@
 
 # App Ideas
 - File viewer (images, text... binary?)
-- GPIO status viewer
 - BlueTooth keyboard app
 - Chip 8 emulator
 - BadUSB

docs/project-structure.puml

@@ -0,0 +1,23 @@
+@startuml
+skinparam componentStyle uml1
+
+[tactility] as t
+note right of t : to build and use graphical apps
+[tactility-headless] as theadless
+note right of theadless : to build and use background services
+[tactility-core] as tcore
+note right of tcore : defines, data types, logging, async, etc.
+
+package "Applications" {
+  [app-sim] as appsim
+  [app-esp] as appesp
+}
+
+note right of appesp : app-esp depends on the board \n projects for configuration
+
+[t] ..> [theadless]
+[theadless] ..> [tcore]
+[appsim] ..> [t]
+[appesp] ..> [t]
+
+@enduml