feat: Initial support for fan-, progress-, & pointer-sensors (#8)

* feat: support progress, fan, pointer sensor types

Initial implementation, not yet fully working.

* only use one rendering layer per sensor type instead one per sensor

Each layer uses > 1 MB and a panel can contain easily over 20 sensors!

* support custom panels with --panels cli argument

This includes one or more additional custom panels into the base
configuration. Multiple --panels arguments are supported

* update docs

doc/sensor_mode1_text.md

@@ -0,0 +1,98 @@
+# Sensor Mode 1 Text
+
+A text sensor renders a text label with a sensor value and an optional unit text on the panel. 
+The value can be formatted as a fixed point decimal number or as an integer.
+
+Text sensor configuration fields:
+- `mode`: 1 (for text)
+- `label`: label identifier, also used as sensor value data source identifier
+- `direction`: 1 = left to right, 2 = right to left, 3 = top to bottom, 4 = bottom to top
+- `label`: data source id to retrieve the current value from
+- `unit`: optional unit label, appended after the sensor value 
+- `x`, `y`: position on the panel
+- `fontFamily`: Font name matching font filename without file extension.
+  - Fonts are loaded from the configured font directory, or from the custom panel's `fonts` directory. 
+  - An absolute file path can also be used.
+- `fontSize`: Font size
+- `fontColor`: Font color in `#RRGGBB` notation, or `-1` if not set.
+  - Examples: `#ffffff` = white, `#ff0000` = red. Default: `#ffffff`
+- `textAlign`: Text alignment: `left`, `center`, `right`
+- `integerDigits`: number of integer digits: -1 or missing field = all digits, > 0 prefix with `0` and set to `9` if overflown
+- `decimalDigits`: number fixed point digits: -1 = auto, 0 = integer number without decimal digits, > 0 fixed number of decimal digits
+
+## Value Formatting
+
+The sensor value can be formatted with the `unit` and `integerDigits` & `decimalDigits` options.
+
+- The unit value is simply appended to the value, without whitespace.
+- Example formatting for the value `123.456` with `integerDigits` & `decimalDigits`:
+
+| integer | decimal | output   |
+|---------|---------|----------|
+| 5       | 2       | 00123.46 |
+| 5       | 1       | 00123.5  |
+| 5       | 0       | 00123    |
+| -1      | 2       | 123.46   |
+| -1      | 1       | 123.5    |
+| -1      | 0       | 123      |
+| 2       | 0       | 99       |
+
+
+## Example
+
+Example `panel.json` with two "text" indicator sensors and the following (partial) background image in `img`:
+
+<img src="img/sensor_mode1_background.png" alt="sensor mode 1 background image example">
+
+The background image and sensor definitions are taken from the default system panel configuration in the AOOSTAR-X app.
+
+```json
+{
+  "name": "Text test panel",
+  "img": "background.png",
+  "sensor": [
+    {
+      "mode": 1,
+      "type": 1,
+      "name": "CPU temp",
+      "label": "cpu_temperature",
+      "x": 195,
+      "y": 110,
+      "value": "65",
+      "fontFamily": "HarmonyOS_Sans_SC_Bold",
+      "fontSize": 120,
+      "fontColor": -1,
+      "textAlign": "center",
+      "decimalDigits": 0
+    },
+    {
+      "mode": 1,
+      "type": 1,
+      "name": "CPU usage",
+      "label": "cpu_percent",
+      "unit": "%",
+      "x": 200,
+      "y": 285,
+      "value": "47.4",
+      "fontFamily": "HarmonyOS_Sans_SC_Bold",
+      "fontSize": 60,
+      "fontColor": -1,
+      "textAlign": "center",
+      "decimalDigits": 0
+    }
+  ]
+}
+```
+
+The following graphic is rendered for the two text fields defined above:
+
+<img src="img/sensor_mode1.png" alt="sensor mode 1 example">
+
+## Known Issues
+
+Text sensor formatting has been reverse engineered from the AOOSTAR-X app. Not all options are supported
+
+- Text position and font size calculation doesn't always match AOOSTAR-X.
+  - Needs investigation if value is in pixel or points.
+  - Might also need dpi adjustments.
+- `fontWeight` not yet supported.