document it

Author: dummdidumm

documentation/docs/05-misc/03-typescript.md

@@ -140,6 +140,24 @@ declare namespace svelteHTML {
 
 Then make sure that `d.ts` file is referenced in your `tsconfig.json`. If it reads something like `"include": ["src/**/*"]` and your `d.ts` file is inside `src`, it should work. You may need to reload for the changes to take effect.
 
+Since Svelte version 4.2 / `svelte-check` version 3.5 / VS Code extension version 107.10.0 you can also declare the typings by augmenting the the `svelte/elements` module like this:
+
+```js
+/// file: additional-svelte-typings.d.ts
+import { HTMLButtonAttributes } from 'svelte/elements'
+
+declare module 'svelte/elements' {
+    export interface SvelteHTMLElements {
+        'custom-button': HTMLButtonAttributes;
+    }
+
+	// allows for more granular control over what element to add the typings to
+    export interface HTMLButtonAttributes {
+        'veryexperimentalattribute'?: string;
+    }
+}
+```
+
 ## Experimental advanced typings
 
 A few features are missing from taking full advantage of TypeScript in more advanced use cases like typing that a component implements a certain interface, explicitly typing slots, or using generics. These things are possible using experimental advanced type capabilities. See [this RFC](https://github.com/dummdidumm/rfcs/blob/ts-typedefs-within-svelte-components/text/ts-typing-props-slots-events.md) for more information on how to make use of them.