[Web, 3.x] Add IME input support.

[bruvzg]

Backport of #79362 (also include #91695 fixes).

[jtakakura]

Thank you for your backport.
It seems to work fine on Firefox.

79362_add_ime_input_support_firefox.mp4

However, upon confirming the Japanese input with the Enter key, a new line is inserted simultaneously on Safari on macOS.

79362_add_ime_input_support_safari.mp4

This could be caused by Safari or Godot; it's not clear which one.

[bruvzg]

This could be caused by Safari or Godot; it's not clear which one.

Seems to be something Safari specific, I can't reproduce it in Chrome or Firefox. Also reproducible with Safari and 4.x.

[JunShiozawa]

How can I check if it works?

[jtakakura]

@JunShiozawa First, you need to check out this PR.
After that, build Godot and its web template.
See the following documents for more details.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally?platform=windows
https://docs.godotengine.org/en/3.6/development/compiling/introduction_to_the_buildsystem.html
https://docs.godotengine.org/en/3.6/development/compiling/compiling_for_web.html

[JunShiozawa]

@akien-mga
Why don't you review this PR?

[akien-mga]

@akien-mga Why don't you review this PR?

I would kindly ask you to stop lobbying maintainers to work on your personal priorities. We are all busy and doing what we can with the time we have.

If you absolutely need this PR today, you can merge it in your own branch and use it, following the documentation that was linked to you above.

If you want to help getting this merged, actually testing it and reporting whether it works on all your target browsers would be very helpful.

[JunShiozawa]

@akien-mga
I am sorry.

[jtakakura]

@JunShiozawa Did you check if it works?
I already explained how to check it.
Will this PR meet your expectations if merged as it is?

[JunShiozawa]

Where is Export templates?
I can not export HTML5.

[JunShiozawa]

This for Godot 4.x Version is
Chrome for Android Japanese input OK.
Firefox for Android Japanese input OK.
Safari for iPhone Japanese input OK.
Firefox for Linux Japanese input OK.
Firefox for Windows Japanese input OK.
Probably it will work.

[akien-mga]

@JunShiozawa Thanks for testing and confirming it works on multiple platforms and browsers.

[akien-mga]

Thanks!