Enable to type t.context by extending module interface

docs/recipes/typescript.md

@@ -151,6 +151,20 @@ test('an actual test', t => {
 });
 ```
 
+Alternatively, you can extend the type globally:
+
+```ts
+declare module 'ava' {
+    interface AvaContext {
+        foo: string;
+    }
+}
+
+test.beforeEach(t => {
+	t.context = {foo: 'bar'};
+});
+```
+
 Note that, despite the type cast above, when executing `t.context` is an empty object unless it's assigned.
 
 ## Typing `throws` assertions

types/test-fn.d.cts

@@ -72,7 +72,9 @@
 /** A test or hook implementation. */
 export type Implementation<Args extends unknown[], Context = unknown> = ImplementationFn<Args, Context> | Macro<Args, Context>;
 
-export type TestFn<Context = unknown> = {
+interface AvaContext {}
+
+export type TestFn<Context = AvaContext> = {
 	/** Declare a concurrent test. Additional arguments are passed to the implementation or macro. */
 	<Args extends unknown[]>(title: string, implementation: Implementation<Args, Context>, ...args: Args): void;