Add description to card metadata

TER (Translation Edit Rate, also called Translation Error Rate) is a metric to quantify the edit operations that a
hypothesis requires to match a reference translation. We use the implementation that is already present in sacrebleu
(https://github.com/mjpost/sacreBLEU#ter), which in turn is inspired by the TERCOM implementation, which can be found
here: https://github.com/jhclark/tercom.

The implementation here is slightly different from sacrebleu in terms of the required input format. The length of
the references and hypotheses lists need to be the same, so you may need to transpose your references compared to
sacrebleu's required input format. See https://github.com/huggingface/datasets/issues/3154#issuecomment-950746534

See the README.md file at https://github.com/mjpost/sacreBLEU#ter for more information.

README.md

@@ -1,6 +1,6 @@
 ---
 title: TER
-emoji: 🤗 
+emoji: 🤗
 colorFrom: blue
 colorTo: red
 sdk: gradio
@@ -8,10 +8,34 @@ sdk_version: 3.0.2
 app_file: app.py
 pinned: false
 tags:
-- evaluate
-- metric
----
+  - evaluate
+  - metric
+description: >-
+  TER (Translation Edit Rate, also called Translation Error Rate) is a metric to
+  quantify the edit operations that a
+
+  hypothesis requires to match a reference translation. We use the
+  implementation that is already present in sacrebleu
+
+  (https://github.com/mjpost/sacreBLEU#ter), which in turn is inspired by the
+  TERCOM implementation, which can be found
+
+  here: https://github.com/jhclark/tercom.
+
 
+  The implementation here is slightly different from sacrebleu in terms of the
+  required input format. The length of
+
+  the references and hypotheses lists need to be the same, so you may need to
+  transpose your references compared to
+
+  sacrebleu's required input format. See
+  https://github.com/huggingface/datasets/issues/3154#issuecomment-950746534
+
+
+  See the README.md file at https://github.com/mjpost/sacreBLEU#ter for more
+  information.
+---
 # Metric Card for TER
 
 ## Metric Description