feat: add markdown editing mode

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/hyperlog-tui/src/project_dirs.rs

@@ -0,0 +1,5 @@
+use directories::ProjectDirs;
+
+pub fn get_project_dir() -> ProjectDirs {
+    ProjectDirs::from("io", "kjuulh", "hyperlog").expect("to be able to get project dirs")
+}