Screenshot app & service (#42)

- Added screenshot app & service (PC-only for now)
- Updated docs with screenshots and new device photo
- Add fake statusbar icons for PC/sim build
- added `lv_screenshot` library based on `lv_100ask_screenshot` from https://github.com/100askTeam/lv_lib_100ask
- T-Deck WiFi is now allocated into SPI RAM
- Created `tt_service_find()` to find services by their id

docs/ideas.md

@@ -7,6 +7,8 @@
 - 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))
 - T-Deck has random sdcard SPI crashes due to sharing bus with screen SPI: make it use the LVGL lock for sdcard operations?
 - Wi-Fi connect app should show info about connection result
+- Check service/app id on registration to see if it is a duplicate id
+- Fix screenshot app on ESP32: it currently blocks when allocating memory
  
 # 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.