feat(puppeteer-core): keydown supports commands (#9357)

Issue: #1313

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**What kind of change does this PR introduce?**

Feature.

**Did you add tests for your changes?**

Yes.

**If relevant, did you update the documentation?**

Yes.

**Summary**

Supports keyboard shotcuts on MacOS. See Chrome Devtools Protocol
document:
https://chromedevtools.github.io/devtools-protocol/tot/Input/#method-dispatchKeyEvent.

test/TestExpectations.json

@@ -569,6 +569,12 @@
     "parameters": ["firefox"],
     "expectations": ["SKIP"]
   },
+  {
+    "testIdPattern": "[keyboard.spec] Keyboard should trigger commands of keyboard shortcuts",
+    "platforms": ["darwin", "linux", "win32"],
+    "parameters": ["firefox"],
+    "expectations": ["SKIP"]
+  },
   {
     "testIdPattern": "[keyboard.spec] Keyboard should report shiftKey",
     "platforms": ["darwin", "linux", "win32"],