Add minimal support for HTML formatting

Just bold/italic/underline for now.

tests/components/backlog.rs

@@ -14,8 +14,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-use std::sync::Arc;
 use std::path::PathBuf;
+use std::sync::Arc;
 
 use color_eyre::eyre::WrapErr;
 use pretty_assertions::assert_eq;