MD Viewer v0.3.0

• Added nested document outline rendering for h1 through h6.
• Added outline navigation in preview, edit, and split modes, including synchronized editor and preview positioning.
• Added support for Markdown heading anchor links, including Chinese and mixed Chinese/English headings.
• Added a back-to-top button for long documents.
• Added workspace context actions to close the current workspace and close loose single files.
• Added multi-window workspace opening when dropping a second folder into an existing workspace window.
• Added full filename tooltips on tabs.
• Improved exports so save dialogs default to the source Markdown folder.
• Improved the academic DOCX export format with 1.5 line spacing, first-line indentation, and compact heading spacing while keeping the app preview style unchanged.
• Improved Windows support with Explorer reveal actions and adaptive startup window sizing.
• Fixed loose single files staying in the sidebar after closing their tabs.
• Fixed compact document outline layout when a document has only a few headings.