Add slot locking

src/main/kotlin/moe/nea/firmament/features/FirmamentFeature.kt

@@ -0,0 +1,18 @@
+package moe.nea.firmament.features
+
+import moe.nea.firmament.util.config.ManagedConfig
+
+interface FirmamentFeature {
+    val name: String
+    val identifier: String
+    val defaultEnabled: Boolean
+        get() = true
+    var isEnabled: Boolean
+        get() = FeatureManager.isEnabled(identifier) ?: defaultEnabled
+        set(value) {
+            FeatureManager.setEnabled(identifier, value)
+        }
+    val config: ManagedConfig? get() = null
+    fun onLoad()
+
+}