console: document the behavior of console.assert()

Add a description and an example of console.assert() call with
no arguments. If called like this, the method should output:
"Assertion failed".

Fixes: #34500
Refs: https://nodejs.org/dist/latest-v14.x/docs/api/console.html#console_console_assert_value_message
Refs: https://console.spec.whatwg.org/#assert

PR-URL: #34501
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>

doc/api/console.md

@@ -151,6 +151,7 @@ changes:
 * `...message` {any} All arguments besides `value` are used as error message.
 
 A simple assertion test that verifies whether `value` is truthy. If it is not,
+or `value` is not passed,
 `Assertion failed` is logged. If provided, the error `message` is formatted
 using [`util.format()`][] by passing along all message arguments. The output is
 used as the error message.
@@ -160,6 +161,8 @@ console.assert(true, 'does nothing');
 // OK
 console.assert(false, 'Whoops %s work', 'didn\'t');
 // Assertion failed: Whoops didn't work
+console.assert();
+// Assertion failed
 ```
 
 Calling `console.assert()` with a falsy assertion will only cause the `message`