Move some versions to gradle.properties; update versions

build.gradle

@@ -1,6 +1,6 @@
 plugins {
     id 'java'
-    id("xyz.jpenilla.run-paper") version "2.3.1"
+    id("xyz.jpenilla.run-paper") version "${runPaperVersion}"
 }
 
 group = 'de.shiewk'
@@ -33,14 +33,14 @@ runServer {
     minecraftVersion("1.21.11")
     downloadPlugins {
         // for testing from other client versions
-        modrinth("ViaVersion", "5.5.1")
-        modrinth("ViaBackwards", "5.5.1")
+        modrinth("ViaVersion", viaVersionVersion)
+        modrinth("ViaBackwards", viaVersionVersion)
     }
 }
 
 dependencies {
-    //compileOnly "io.papermc.paper:paper-api:1.21.4-R0.1-SNAPSHOT"
-    compileOnly 'dev.folia:folia-api:1.21.4-R0.1-SNAPSHOT'
+    //compileOnly "io.papermc.paper:paper-api:${apiVersion}"
+    compileOnly "dev.folia:folia-api:${apiVersion}"
 }
 
 jar {