Fix #637 : Markdown footnotes (#700)

* Ensure footnotes classes generated are not filtered

pulldown-cmark add somes classes when footnotes html is generated. This commit ensure they are not filtered by html sanitizer

* Add some footnotes styling

plume-models/src/safe_string.rs

@@ -31,6 +31,9 @@ lazy_static! {
             .add_tag_attributes("label", ["for"].iter())
             .add_tag_attributes("input", ["type", "checked"].iter())
             .add_allowed_classes("input", ["cw-checkbox"].iter())
+            // Related to https://github.com/Plume-org/Plume/issues/637
+            .add_allowed_classes("sup", ["footnote-reference", "footnote-definition-label"].iter())
+            .add_allowed_classes("div", ["footnote-definition"].iter())
             .add_allowed_classes("span", ["cw-container", "cw-text"].iter())
             .attribute_filter(|elem, att, val| match (elem, att) {
                 ("input", "type") => Some("checkbox".into()),