Fix image names

src/main/kotlin/process.kt

@@ -76,7 +76,7 @@ internal suspend fun SpaceClient.processMarkdownDocument(path: Path) = coroutine
     val newText = documentBody.replace(regex) {
         val id = it.groups["id"]?.value ?: error("Unexpected reference format: ${it.value}")
         val alt = it.groups["alt"]?.value
-        val imageName = alt ?: id
+        val imageName = alt?.let { "$id-$alt" } ?: id
         logger.info("Downloading image $id as images/$imageName")
         launch(Dispatchers.IO) {
             extractImage(path.parent, id, imageName)