Geo-Compose: Add module README (#294)

* add readme and screenshot to geo-compose module

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Author: hud10837

toolkit/geo-compose/README.md

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+# Geo-Compose
+
+The Geo-Compose module provides `@Composable` implementations of the `MapView` and `SceneView` with a Compose-idiomatic API.
+
+|Geo-Compose|
+|:--:|
+|![image](screenshot.png)|
+
+## Features
+
+### Display a Map
+
+Displaying a map on the screen looks like this:
+
+```kotlin
+val arcGISMap = remember { ArcGISMap(BasemapStyle.ArcGISImagery) }
+MapView(
+	modifier = Modifier.fillMaxSize(),
+	arcGISMap = arcGISMap
+)
+```
+
+### Respond to User Input
+
+The composable `MapView` and `SceneView` expose gesture events as lambda callback parameters:
+
+```kotlin
+val arcGISMap = remember { ArcGISMap(BasemapStyle.ArcGISImagery) }
+MapView(
+	modifier = Modifier.fillMaxSize(),
+	arcGISMap = arcGISMap,
+	onSingleTapConfirmed = { singleTapConfirmedEvent ->
+		val x = singleTapConfirmedEvent.screenCoordinate.x
+		val y = singleTapConfirmedEvent.screenCoordinate.y
+		Log.i("MapView", "Single tap at $x, $y")
+	}
+)
+```
+
+### Set a Viewpoint
+
+Setting the viewpoint of the `MapView` is handled by a parameter to the composable function.
+
+```kotlin
+val point = Point(-117.182541, 34.055569, SpatialReference.wgs84())
+val scale = 170000.0
+val viewpointOperation = remember { MapViewpointOperation.Set(Viewpoint(point, scale)) }
+
+MapView(
+	modifier = Modifier.fillMaxSize(),
+	arcGISMap = remember { ArcGISMap(BasemapStyle.ArcGISImagery) },
+	viewpointOperation = viewpointOperation
+)
+```
+
+Examples of how to use `MapViewpointOperation` and `SceneViewpointOperation` are available in the respective microapps:
+
+- [MapView Set Viewpoint App](../../microapps/MapViewSetViewpointApp/README.md)
+- [SceneView Set Viewpoint App](../../microapps/SceneViewSetViewpointApp/README.md)
+
+### Display the Device Location
+
+A `LocationDisplay` can be used to display the device's location as a blue dot on a `MapView`:
+
+```kotlin
+val arcGISMap = remember { ArcGISMap(BasemapStyle.ArcGISImagery) }
+val scope = rememberCoroutineScope()
+val locationDisplay = rememberLocationDisplay {
+	start(scope)
+}
+MapView(
+	modifier = Modifier.fillMaxSize(),
+	arcGISMap = remember { ArcGISMap(BasemapStyle.ArcGISImagery) },
+	locationDisplay = locationDisplay
+)
+```
+
+An example of how to display the device location is available in the [MapView Location Display App](../../microapps/MapViewLocationDisplayApp/README.md).
+
+### Identify a Feature
+
+To identify a feature, create a `MapViewProxy` and call `identify()` on it after the `MapView` is displayed on screen
+
+```kotlin
+val mapViewProxy = remember { MapViewProxy() }
+val arcGISMap = remember { ArcGISMap(BasemapStyle.ArcGISImagery) }
+val scope = rememberCoroutineScope()
+MapView(
+	modifier = Modifier.fillMaxSize(),
+	arcGISMap = arcGISMap,
+	mapViewProxy = mapViewProxy,
+	onSingleTapConfirmed = { singleTapConfirmedEvent ->
+		scope.launch {
+			mapViewProxy.identify(featureLayer, singleTapConfirmedEvent.screenCoordinate, 20.dp)
+		}
+	}
+)
+```
+
+An example of how to identify features and graphics is available in the [MapView Identify App](../../microapps/MapViewIdentifyApp/README.md).
+
+### Other Examples:
+
+Other microapps that demonstrate various workflows with the composable `MapView` and `SceneView` are available:
+
+- [MapView Geometry Editor App](../../microapps/MapViewGeometryEditorApp/README.md) demonstrates the use of `GeometryEditor` and `GraphicsOverlay`
+- [MapView Insets App](../../microapps/MapViewInsetsApp/README.md) demonstrates the use of `Insets`
+- [SceneView Camera Controller App](../../microapps/SceneViewCameraControllerApp/README.md) demonstrates the use of the `CameraController`
+- [SceneView Lighting Options App](../../microapps/SceneViewLightingOptionsApp/README.md) demonstrates the use of various lighting options with the `SceneView`
+
+