Loosen up types for (un)watchedc (#688)

Author: JoviDeCroock

.changeset/breezy-cherries-type.md

@@ -0,0 +1,5 @@
+---
+"@preact/signals-core": patch
+---
+
+Loosen up types for `watched` and `unwatched`

packages/core/src/index.ts

@@ -273,8 +273,8 @@ declare class Signal<T = any> {
 }
 
 export interface SignalOptions<T = any> {
-	watched: (this: Signal<T>) => void;
-	unwatched: (this: Signal<T>) => void;
+	watched?: (this: Signal<T>) => void;
+	unwatched?: (this: Signal<T>) => void;
 }
 
 /** @internal */