Customization: mention completion.placeholder

Customization.md

@@ -149,15 +149,20 @@ Use the path provided as the Clang resource directory rather the default.  See
 information.
 
 #### `client.snippetSupport`
+#### `completion.placeholder`
 
-Default: `true`
+`client.snippetSupport` (default: `true`) and `completion.placeholder` (default: `true`)
+decide the completion style.
 
-LSP snippets in completion items are enabled if this option is true and the
-client announces that it supports it
-(`capabilities.textDocument.completionItem.snippetSupport`). If your client
-supports LSP snippets but you don't like them, set the option to `false`.
+* client.snippetSupport: false => `foo`
+* client.snippetSupport: true
+  + completion.placeholder: false => `foo($1)$0` `bar<$1>()$0`
+  + completion.placeholder: true => `foo(${1:int a}, ${2:int b})$0` `bar<${1:typename T}>()$0`
 
-Example: `{"client": {"snippetSupport": false}}`
+If the client announces that it does not support snippets,
+`client.snippetSupport` will be forced to false.
+
+Example: `{"client": {"snippetSupport": true}, "completion": {"placeholder": false}}`
 
 #### `compilationDatabaseDirectory`