Replace or remove flutter_keyboard_visibility plugin from flutter_quill

[EchoEllet]

It seems that flutter_keyboard_visibility hasn't been updated for a while, having PRs on hold for one or two years that already fixed some issues:

• Support for Flutter/WASM: it seems that this plugin doesn't support web platform for mobile, instead it returns false and uses dart:html which is being replaced by web package, this is a critical issue for users to migrate their projects to new technologies, while we don't use Flutter/WASM, we don't want to have any blockers or obstacles for the users of this project, a minimal [PR Fixes crashing disposed listeners on a bunch of widgets #164]. Also, see PR #155 which adds experimental support for the web. Related issue Cannot build to WASM with flutter_quill #1889
  (https://www.github.com/MisterJimson/flutter_keyboard_visibility/pull/164) is already made
• Always using 31 for compileSdkVersion on Android: Due to an internal bug in Flutter (see Flutter #63533), plugins that hardcode the compileSdkVersion will force the app project to not being able to target newer versions of compileSdkVersion, the latest is 34, while this may sound not important for some users, Google play may require targeting newer versions of Android for publishing the app. Better solve this issue sooner than later. A minimal PR #159 is already sent.
• Not supporting recent Android API: This may sound not an issue at all for most users, however usually native Android apps do use newer APIs when available, and fall to the older API (even if not deprecated) for older versions, see #120.
• Not being updated for 2 years: It seems only minor changes have been introduced for the last 2 years, in general, we prefer something that's more stable and published less often, however, it seems that new issues and PRs are not being replied on, which might cause issues for the users.

We do want to remove more dependencies, especially heavy or outdated plugins, allowing the users to use flutter_quill as a dependency without conflicting or depending on other dependencies so they can choose the dependencies they want to have.

Removing a feature to fix a bug is not the solution will be used here, instead we will find another alternative, if not, we will write our own solution in quill_native_bridge or completely have a separate plugin for this functionality, this feature is usually only required on mobile platforms, which make it less time expensive to implement.

[EchoEllet]

We're currently still in the middle of #2230. Once it's done, spell spell-checking issue is addressed, and many other issues, we will start on fixing this issue.