Configure maven central snapshot versions for the Godot Android library

A snapshot version is a version that has not yet been released which allows us to deploy the same transient version incrementally, without requiring projects to upgrade the artifact version they're consuming. Those projects can use the same version to get an updated snapshot version.

platform/android/java/app/config.gradle

@@ -189,6 +189,9 @@ ext.getGodotPublishVersion = { ->
     String versionName = ""
     int versionCode = 1
     (versionName, versionCode) = generateGodotLibraryVersion(requiredKeys)
+    if (!versionName.endsWith("stable")) {
+        versionName += "-SNAPSHOT"
+    }
     return versionName
 }