Berry debug_panel.tapp to display real-time heap and wifi rssi

[s-hadinger]

Description:

After the nice innovation brought by GPIO Viewer, I propose a simple debug_panel.tapp Berry application to display real-time heap size and wifi rssi on top of the web UI. This is still a proof-of-concept. It uses full async non-blocking communication so it shouldn't hurt the performance and responsiveness of Tasmota.

It requires the latest development version.

To use, just copy debug_panel.tapp in the file system and restart.

Demo_debug_panel.mov

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.14
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass