Change paper-api to a non-required dependency

Allows forks to be used instead of being stuck to use paper-api

Author: Aeltumn

interfaces/build.gradle.kts

@@ -5,10 +5,14 @@ plugins {
 
 dependencies {
     compileOnlyApi(libs.adventure.api)
-    compileOnlyApi(libs.paper.api) {
+    compileOnlyApi(libs.guava)
+
+    // Paper-api is not marked as api, it is expected that
+    // some version of Paper is present in the final plugin!
+    // But this may be some fork instead of the regular paper.
+    compileOnly(libs.paper.api) {
         isTransitive = false
     }
-    compileOnlyApi(libs.guava)
 
     api(libs.kotlin.coroutines)
     api(libs.slf4j)