feat: Add a custom reaction popup and some fixes

[kreativityapps]

Description

Added the possibility to specify a customReactionPopup. This can be used instead of emojis when long pressing on a message, for example it can be used to show a menu. It also returns the message which was pressed.
I used Listener, so both widget.onTap and also external taps can be handled from customReactionPopup.

Added also possibility to set the borderRadius for the popup.

Added possibility to set autofocus for the text field. Default is false.

Fixed issue with trying to submit a message by pressing enter in the keyboard, now onSubmit calls _onPressed, sending the message.

Fixed issue with the reaction popup config, ConfigurationsInheritedWidget had to be moved up to contain also the ReactionPopup, this way the config here won't be null anymore and all reaction popup configs will work, see #261

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

Closes #261