fix(doc): add missing test runner option

PR-URL: nodejs/node#43989
Refs: nodejs/node#43554
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Darshan Sen <[email protected]>
(cherry picked from commit 7a18ee8315ecc8ad1a1316ff1c951694f8e8f7a4)

Author: MoLow

README.md

@@ -506,6 +506,7 @@ execution of the test function. This function does not return a value.
   - `skip` {boolean|string} If truthy, the test is skipped. If a string is
     provided, that string is displayed in the test results as the reason for
     skipping the test. **Default:** `false`.
+  - `signal` {AbortSignal} Allows aborting an in-progress test
   - `todo` {boolean|string} If truthy, the test marked as `TODO`. If a string
     is provided, that string is displayed in the test results as the reason why
     the test is `TODO`. **Default:** `false`.