dsh-plugin-file-and-terminal: Adding File Management and Terminal Panels to DSH Web Configuration

`dsh-plugin-file-and-terminal` is an open-source plugin maintained by CarrotFish, designed to provide file management and terminal capabilities to the DSH Web environment, addressing the limitations of native Web configurations that lack these features. Key capabilities include in-browser file system browsing, upload/download of directories and files, and support for symbolic links. It also provides an interactive Bash terminal based on xterm.js, with persistent session state across transitions. The plugin runs with DSH process privileges and can only access configured root directories, so it is recommended to be enabled in trusted environments. After installation, it works in conjunction with `dsh-better-sidebar` to share state between the sidebar and the main panel.