docs(angular): update version compatibility table (#1522)

Author: timdeschryver

docs/angular-testing-library/version-compatibility.mdx

@@ -8,8 +8,9 @@ Library and Angular.
 
 | Angular | Angular Testing Library            |
 | ------- | ---------------------------------- |
-| 20.x    | 18.x                               |
-| 19.x    | 18.x, 17.x, 16.x, 15.x, 14.x, 13.x |
+| 21.x    | 19.x                               |
+| 20.x    | 18.x, 17.x, 16.x, 15.x, 14.x, 13.x |
+| 19.x    | 17.x, 16.x, 15.x, 14.x, 13.x       |
 | 18.x    | 17.x, 16.x, 15.x, 14.x, 13.x       |
 | 17.x    | 17.x, 16.x, 15.x, 14.x, 13.x       |
 | 16.x    | 14.x, 13.x                         |