feat(editor): 增加MD文件预览功能 - #522

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-go@v3. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Include file: <QDir> not found. Please note: Cppcheck does not need standard library headers to get proper results.

Include file: <unistd.h> not found. Please note: Cppcheck does not need standard library headers to get proper results.

Include file: "drecentmanager.h" not found.

Variable 'shortcuts_editor_backindentlineName' is assigned a value that is never used.

Variable 'shortcuts_editor_indentlineName' is assigned a value that is never used.

Variable 'group_editorName' is assigned a value that is never used.

Variable 'shortcuts_window_togglemarkdownpreviewName' is assigned a value that is never used.

Variable 'shortcuts_window_printName' is assigned a value that is never used.

Variable 'shortcuts_window_displayshortcutsName' is assigned a value that is never used.