Initial solid polygon layer docs (#69)

docs/layers/scatterplot-layer.md

@@ -10,6 +10,7 @@ The `ScatterplotLayer` renders circles at given coordinates.
 import geopandas as gpd
 from lonboard import ScatterplotLayer
 
+# A GeoDataFrame with Point geometries
 gdf = gpd.GeoDataFrame()
 layer = ScatterplotLayer.from_geopandas(
     gdf,

docs/layers/solid-polygon-layer.md

@@ -0,0 +1,98 @@
+# SolidPolygonLayer
+
+The `SolidPolygonLayer` renders filled and/or extruded polygons.
+
+```py
+import geopandas as gpd
+from lonboard import SolidPolygonLayer
+
+# A GeoDataFrame with Polygon geometries
+gdf = gpd.GeoDataFrame()
+layer = SolidPolygonLayer.from_geopandas(
+    gdf,
+    get_fill_color=[255, 0, 0],
+)
+```
+
+## Properties
+
+<!-- Inherits from all [Base Layer](../core/layer.md) properties. -->
+
+### Render Options
+
+#### `filled`
+
+- Type: `bool`, optional
+- Default: `True`
+
+Whether to fill the polygons (based on the color provided by the
+`get_fill_color` accessor).
+
+#### `extruded`
+
+- Type: `bool`, optional
+- Default: `False`
+
+Whether to extrude the polygons (based on the elevations provided by the
+`get_elevation` accessor'). If set to false, all polygons will be flat, this
+generates less geometry and is faster than simply returning `0` from `get_elevation`.
+
+#### `wireframe`
+
+- Type: `bool`, optional
+- Default: `False`
+
+Whether to generate a line wireframe of the polygon. The outline will have
+"horizontal" lines closing the top and bottom polygons and a vertical line
+(a "strut") for each vertex on the polygon.
+
+#### `elevation_scale`
+
+- (Number, optional)
+- Default: `1`
+
+Elevation multiplier. The final elevation is calculated by
+  `elevation_scale * get_elevation(d)`. `elevation_scale` is a handy property to scale
+all elevation without updating the data.
+
+-*Remarks:**
+
+- These lines are rendered with `GL.LINE` and will thus always be 1 pixel wide.
+- Wireframe and solid extrusions are exclusive, you'll need to create two layers
+  with the same data if you want a combined rendering effect.
+
+### Data Accessors
+
+#### `get_fill_color`
+
+- Type: (Array, optional)
+- Default: `[0, 0, 0, 255]`
+
+The rgba color is in the format of `[r, g, b, [a]]`. Each channel is a number between 0-255 and `a` is 255 if not supplied.
+
+- If an array is provided, it is used as the fill color for all polygons.
+- If a function is provided, it is called on each polygon to retrieve its fill color.
+
+#### `get_line_color`
+
+- Type: (Array, optional)
+- Default: `[0, 0, 0, 255]`
+
+The rgba color is in the format of `[r, g, b, [a]]`. Each channel is a number between 0-255 and `a` is 255 if not supplied.
+Only applies if `extruded: true`.
+
+- If an array is provided, it is used as the stroke color for all polygons.
+- If a function is provided, it is called on each object to retrieve its stroke color.
+
+#### `get_elevation`
+
+- Type: (Number, optional)
+- Default: `1000`
+
+The elevation to extrude each polygon with.
+If a cartographic projection mode is used, height will be interpreted as meters,
+otherwise will be in unit coordinates.
+Only applies if `extruded: true`.
+
+- If a number is provided, it is used as the elevation for all polygons.
+- If a function is provided, it is called on each object to retrieve its elevation.