feat: KaTeX数式サポートを追加（marked-katex-extension使用）

Merge pull request #2 from demitas1/feature/#1-img-html-tag

feat: support <img> tag with local image Base64 conversion and style attributes (#1)

bugfix: switch themes

fix: open http url by external browser

fix: relative file link

fix: navigate correct file link

restore position after hot reload

feature: image

feature: hot reload

mermaid support

theme switch, default md

build and run script

init