Add description to card metadata

The F1 score is the harmonic mean of the precision and recall. It can be computed with the equation:
F1 = 2 * (precision * recall) / (precision + recall)

README.md

@@ -1,6 +1,6 @@
 ---
 title: F1
-emoji: 🤗 
+emoji: 🤗
 colorFrom: blue
 colorTo: red
 sdk: gradio
@@ -8,10 +8,14 @@ sdk_version: 3.0.2
 app_file: app.py
 pinned: false
 tags:
-- evaluate
-- metric
----
+  - evaluate
+  - metric
+description: >-
+  The F1 score is the harmonic mean of the precision and recall. It can be
+  computed with the equation:
 
+  F1 = 2 * (precision * recall) / (precision + recall)
+---
 # Metric Card for F1