Add docs about initialization options

Author: daplf

README.md

@@ -88,6 +88,10 @@ There is an extensive suite of behavioral [tests](server/src/test/kotlin/org/jav
 
 The Kotlin language server supports some non-standard requests through LSP. See [KotlinProtocolExtensions](server/src/main/kotlin/org/javacs/kt/KotlinProtocolExtensions.kt) for a description of the interface. The general syntax for these methods is `kotlin/someCustomMethod`.
 
+## Initialization Options
+
+The Kotlin language server supports some custom initialization options via the `initializationOptions` property in the `initialize` request parameters. See `InitializationOptions` in [Configuration](server/src/main/kotlin/org/javacs/kt/Configuration.kt) for a list of supported properties.
+
 ## Features
 
 ### Autocomplete

server/src/main/kotlin/org/javacs/kt/Configuration.kt

@@ -58,7 +58,10 @@ fun getStoragePath(params: InitializeParams): Path? {
     return null
 }
 
-data class InitializationOptions(val storagePath: Path?)
+data class InitializationOptions(
+    // A path to a directory used by the language server to store data. Used for caching purposes.
+    val storagePath: Path?
+)
 
 class GsonPathConverter : JsonDeserializer<Path?> {