Pandoc-filter

Fix bugs in `md2md_norm_footnote_filter` to avoid missing links in the footnote content.

Adjusted organization of README.md and RELEASE.md.
Examples were separated out.

Change logging modes in `md2md_convert_github_style_alert_to_hexo_style_alert_filter`.

Fix logging bugs in `md2md_convert_github_style_alert_to_hexo_style_alert_filter`.

Add `md2md_convert_github_style_alert_to_hexo_style_alert_filter`, which can convert the [github-style alert](https://github.com/orgs/community/discussions/16925) to hexo-style alert.The github-style alert is based on pandoc's `BlockQuote` element, while the hexo-style alert is based on [hexo tag plugins](https://hexo.io/docs/tag-plugins#Note).We use a general mode to confirm the hexo-style alert type, which are widely used in the hexo community by many themes, such as
- [hexo-theme-butterfly](https://butterfly.js.org/posts/4aa8abbe/?highlight=%25+endnote#%E6%A8%99%E7%B1%A4%E5%A4%96%E6%8E%9B%EF%BC%88Tag-Plugins%EF%BC%89),
- [hexo-theme-fluid](https://hexo.fluid-dev.com/docs/guide/#tag-%E6%8F%92%E4%BB%B6),
- [hexo-them-next](https://theme-next.js.org/docs/tag-plugins/note).

Re-organize the inner implementation about decoding url.