feat: can create root

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

crates/hyperlog-core/src/engine.rs

@@ -196,6 +196,15 @@ impl Engine {
 
         Ok(())
     }
+
+    pub fn get_roots(&self) -> Option<Vec<String>> {
+        let items = self.graph.keys().cloned().collect::<Vec<_>>();
+        if items.is_empty() {
+            None
+        } else {
+            Some(items)
+        }
+    }
 }
 
 impl Display for Engine {

crates/hyperlog-core/src/querier.rs

@@ -9,6 +9,10 @@ impl Querier {
         Self { engine }
     }
 
+    pub fn get_available_roots(&self) -> Option<Vec<String>> {
+        self.engine.get_roots()
+    }
+
     pub fn get(
         &self,
         root: &str,

crates/hyperlog-core/src/shared_engine.rs

@@ -63,4 +63,8 @@ impl SharedEngine {
 
         Ok(())
     }
+
+    pub(crate) fn get_roots(&self) -> Option<Vec<String>> {
+        self.inner.read().unwrap().get_roots()
+    }
 }