Add description to card metadata

Recall is the fraction of the positive examples that were correctly labeled by the model as positive. It can be computed with the equation:
Recall = TP / (TP + FN)
Where TP is the true positives and FN is the false negatives.

README.md

@@ -1,6 +1,6 @@
 ---
 title: Recall
-emoji: 🤗 
+emoji: 🤗
 colorFrom: blue
 colorTo: red
 sdk: gradio
@@ -8,10 +8,16 @@ sdk_version: 3.0.2
 app_file: app.py
 pinned: false
 tags:
-- evaluate
-- metric
----
+  - evaluate
+  - metric
+description: >-
+  Recall is the fraction of the positive examples that were correctly labeled by
+  the model as positive. It can be computed with the equation:
+
+  Recall = TP / (TP + FN)
 
+  Where TP is the true positives and FN is the false negatives.
+---
 # Metric Card for Recall