essential-loader: improve error message

Author: Sychic

src/main/kotlin/gg/essential/essential-loader.gradle.kts

@@ -36,9 +36,9 @@ when {
     platform.isModLauncher -> {
         dependencies {
             val relocatedPackage = findProperty("essential.loader.package")?.toString() ?: throw GradleException("""
-                No essential loader package set.
-                You need to set `essential.loader.package` in the project's `gradle.properties` file to a specific package.
-                The recommended package is your mod's package.
+                A package for the Essential loader to be relocated to has not been set.
+                You need to set `essential.loader.package` in the project's `gradle.properties` file to a specific package where Essential's loader will be relocated to.
+                The recommended package is an unused package within your mod's package.
             """.trimIndent())
             val relocationAttribute =
                 registerRelocationAttribute("essential-loader-relocated") {