Ignore ENTER while in text composition mode

[compulim]

Fixes #5461.

Changelog Entry

Fixed

• Fixed #5461. On macOS and Fluent skinpack applied, using Japanese IME to input some Japanese text should not send them immediately, in PR #5462, by @compulim

Description

ENTER should not send messages if it is in IME text composition mode.

Design

When browser say they are in text composition mode, it means the IME mini-dialog pops up.

While in text composition mode, ENTER key should not be handled by the browser.

On Windows, when IME mini-dialog pops up, all keys are filtered and will not send to the browser.

On macOS, keys are not (completely) filtered.

In the send box of our Fluent skin pack, it use a multiline textbox (<textarea>) and send on ENTER (new line on SHIFT + ENTER). As macOS did not filter out ENTER, we mistakenly send out the message.

We could not write tests as the behavior works outside of browser and emulating compositionstart event didn't work.

Specific Changes

• Disable send out the message when ENTER is pressed during compositionstart until compositionend

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[OEvgeny]

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