feat: add auto expanded editor showcase

[LucasXu0]

Add an example showcase to set up an auto-expanded editor

showcase.mp4

Code

    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.black,
        title: const Text('Custom Theme For Editor'),
        titleTextStyle: const TextStyle(color: Colors.white),
        iconTheme: const IconThemeData(
          color: Colors.white,
        ),
      ),
      body: SafeArea(
        child: Center(
          child: IntrinsicHeight(
            child: Container(
              alignment: Alignment.center,
              decoration: BoxDecoration(
                border: Border.all(color: Colors.grey),
              ),
              constraints: const BoxConstraints(
                maxHeight: 360,
                maxWidth: 400,
              ),
              child: SingleChildScrollView(
                child: IntrinsicHeight(
                  child: AppFlowyEditor(
                    editorState: editorState,
                    disableAutoScroll: true,
                    shrinkWrap: true,
                    editorStyle: const EditorStyle.desktop(
                      padding: EdgeInsets.symmetric(horizontal: 8),
                    ),
                    blockComponentBuilders: _buildBlockComponentBuilders(),
                    editorScrollController: EditorScrollController(
                      editorState: editorState,
                      shrinkWrap: true,
                    ),
                  ),
                ),
              ),
            ),
          ),
        ),
      ),
    );

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.06%. Comparing base (0a0d441) to head (1920705).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #920   +/-   ##
=======================================
  Coverage   72.06%   72.06%           
=======================================
  Files         318      318           
  Lines       15000    15000           
=======================================
  Hits        10810    10810           
  Misses       4190     4190           

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