Feature variants (#376)

Migrate from buildSrc to build-logic. Setup feature variants.

build-logic/orx-convention/src/preload/kotlin/ApplicationPreload.kt

@@ -0,0 +1,14 @@
+package org.openrndr
+
+import org.openrndr.extensions.SingleScreenshot
+
+/**
+ * This [Preload] class is used by the [CollectScreenshots] task to inject the [SingleScreenshot] extension
+ */
+class Preload : ApplicationPreload() {
+    override fun onProgramSetup(program: Program) {
+        program.extend(SingleScreenshot()) {
+            this.outputFile = System.getProperty("screenshotPath")
+        }
+    }
+}