[orx-camera] Re-add Camera2D (#275)

orx-camera/src/demo/kotlin/DemoCamera2D.kt

@@ -0,0 +1,25 @@
+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.draw.loadFont
+import org.openrndr.extra.camera.Camera2D
+
+/**
+ * # Camera2D demo
+ *
+ * click and drag the mouse for panning, use the mouse wheel for zooming
+ */
+fun main() = application {
+    program {
+        val font = loadFont("demo-data/fonts/IBMPlexMono-Regular.ttf", 72.0)
+
+        extend(Camera2D())
+        extend {
+            drawer.circle(drawer.bounds.center, 300.0)
+
+            drawer.fontMap = font
+            drawer.fill = ColorRGBa.PINK
+            drawer.text("click and drag mouse", 50.0, 400.0)
+            drawer.text("use mouse wheel", 50.0, 500.0)
+        }
+    }
+}