Add md-footnote

crates/lib/md-footnote/README.md

@@ -0,0 +1,59 @@
+# markdown-it-footnote.rs
+
+[<img alt="crates.io" src="https://img.shields.io/crates/v/markdown-it-footnote.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/markdown-it-footnote)
+
+A [markdown-it.rs](https://crates.io/crates/markdown-it) plugin to process footnotes.
+
+It is based on the [pandoc definition](http://johnmacfarlane.net/pandoc/README.html#footnotes):
+
+```md
+Normal footnote:
+
+Here is a footnote reference,[^1] and another.[^longnote]
+
+Here is an inline note.^[my note is here!]
+
+[^1]: Here is the footnote.
+
+[^longnote]: Here's one with multiple blocks.
+
+    Subsequent paragraphs are indented to show that they
+belong to the previous footnote.
+```
+
+See the [tests](tests/fixtures) for more examples.
+
+## Usage
+
+To load the full plugin:
+
+```rust
+let parser = &mut markdown_it::MarkdownIt::new();
+markdown_it::plugins::cmark::add(parser);
+
+md_footnote::add(parser);
+
+let ast  = parser.parse("Example^[my note]");
+let html = ast.render();
+```
+
+Alternatively, you can load the separate components:
+
+```rust
+let parser = &mut markdown_it::MarkdownIt::new();
+markdown_it::plugins::cmark::add(parser);
+
+md_footnote::definitions::add(md);
+md_footnote::references::add(md);
+md_footnote::inline::add(md);
+md_footnote::collect::add(md);
+md_footnote::back_refs::add(md);
+```
+
+Which have the following roles:
+
+- `definitions`: parse footnote definitions, e.g. `[^1]: foo`
+- `references`: parse footnote references, e.g. `[^1]`
+- `inline`: parse inline footnotes, e.g. `^[foo]`
+- `collect`: collect footnote definitions (removing duplicate/unreferenced ones) and move them to be the last child of the root node.
+- `back_refs`: add anchor(s) to footnote definitions, with links back to the reference(s)