Add support for annotations

This matches the taskwarrior task model for annotations.

cli/src/invocation/cmd/info.rs

@@ -39,6 +39,11 @@ pub(crate) fn execute<W: WriteColor>(
             if let Some(wait) = task.get_wait() {
                 t.add_row(row![b->"Wait", wait]);
             }
+            let mut annotations: Vec<_> = task.get_annotations().collect();
+            annotations.sort();
+            for ann in annotations {
+                t.add_row(row![b->"Annotation", format!("{}: {}", ann.entry, ann.description)]);
+            }
         }
         t.print(w)?;
     }

cli/src/invocation/modify.rs

@@ -1,5 +1,6 @@
 use crate::argparse::{DescriptionMod, Modification};
-use taskchampion::TaskMut;
+use chrono::Utc;
+use taskchampion::{Annotation, TaskMut};
 
 /// Apply the given modification
 pub(super) fn apply_modification(
@@ -41,5 +42,12 @@ pub(super) fn apply_modification(
         task.set_wait(wait)?;
     }
 
+    if let Some(ref ann) = modification.annotate {
+        task.add_annotation(Annotation {
+            entry: Utc::now(),
+            description: ann.into(),
+        })?;
+    }
+
     Ok(())
 }