docs: note when init hook was added (#13138)

* docs: note when `init` hook was added

* add `@since` tags

* on second thoughts, just use the tags

Author: Rich-Harris

packages/kit/src/exports/public.d.ts

@@ -726,11 +726,13 @@ export type HandleFetch = (input: {
 
 /**
  * The [`init`](https://svelte.dev/docs/kit/hooks#Shared-hooks-init) will be invoked before the server responds to its first request
+ * @since 2.10.0
  */
 export type ServerInit = () => MaybePromise<void>;
 
 /**
  * The [`init`](https://svelte.dev/docs/kit/hooks#Shared-hooks-init) will be invoked once the app starts in the browser
+ * @since 2.10.0
  */
 export type ClientInit = () => MaybePromise<void>;
 

packages/kit/types/index.d.ts

@@ -708,11 +708,13 @@ declare module '@sveltejs/kit' {
 
 	/**
 	 * The [`init`](https://svelte.dev/docs/kit/hooks#Shared-hooks-init) will be invoked before the server responds to its first request
+	 * @since 2.10.0
 	 */
 	export type ServerInit = () => MaybePromise<void>;
 
 	/**
 	 * The [`init`](https://svelte.dev/docs/kit/hooks#Shared-hooks-init) will be invoked once the app starts in the browser
+	 * @since 2.10.0
 	 */
 	export type ClientInit = () => MaybePromise<void>;