(feat): Composition support for keyboard.imeSetComposition

[trueadm]

Notes:

• Based off the work from (feat): Composition support with keyboard.imeSetComposition, keyboard.imeCancelComposition and keyboard.imeCommitComposition #7487.
• Related feature thread: [Feature] IME support #5777
• Chromium changes have already been merged: https://chromium-review.googlesource.com/c/chromium/src/+/3009937

This PR implements the keyboard composition API keyboard.imeSetComposition. This makes it possible to test low-level IME related composition interactions.

Example:

  await page.focus('textarea');
  await page.keyboard.imeSetComposition('ｓ', 1, 1);
  await page.keyboard.imeSetComposition('す', 1, 1);
  await page.keyboard.imeSetComposition('すｓ', 2, 2);
  await page.keyboard.imeSetComposition('すｓｈ', 3, 3);
  await page.keyboard.imeSetComposition('すし', 2, 2);
  await page.keyboard.insertText('すし');

You might be wondering what, what about triggering of keyboard events such as keyboard.up, keyboard.press, keyboard.down etc, Rather than couple this PR with other discussions (see #7659) I think this can be worked on separately. Having imeSetComposition available sooner will be invaluable right now and help inform us of the discussions around how key events should work, and what their API should be.

[ghost]

All CLA requirements met.

[pavelfeldman]

Closing as stale due to no progress (on our side). I'm not sure the action for this should be, but it seems like we aren't ready for ime API at this point.

[trueadm]

@pavelfeldman Has there been any further interest in adding the IME/Composition API internally. I was of the understanding that this was regarded as important from the Microsoft Editor folks?