Update paddlenlp.metrics README (#5010)

* Update paddlenlp.metrics README

* Add info for Mcc

* delete DuReader metric

* update task name, add API col

PaddleNLP/paddlenlp/metrics/README.md

 # paddlenlp.metrics
 
-## Perplexity
-Perplexity is calculated using cross entropy. It supports both padding data
-and no padding data.
-
-If data is not padded, users should provide `seq_len` for `Metric`
-initialization. If data is padded, your label should contain `seq_mask`,
-which indicates the actual length of samples.
-
-This Perplexity requires that the output of your network is prediction,
-label and sequence length (opitonal). If the Perplexity here doesn't meet
-your needs, you could override the `compute` or `update` method for
-caculating Perplexity.
-
-## BLEU
-BLEU (bilingual evaluation understudy) is an algorithm for evaluating the
-quality of text which has been machine-translated from one natural language
-to another. This metric uses a modified form of precision to compare a
-candidate translation against multiple reference translations.
-
-BLEU could be used as `paddle.metrics.Metric` class, or an ordinary
-class.
-
-When BLEU is used as `paddle.metrics.Metric` class. A function is
-needed that transforms the network output to reference string list, and
-transforms the label to candidate string. By default, a default function
-`_default_trans_func` is provided, which gets target sequence id by
-calculating the maximum probability of each step. In this case, user must
-provide `vocab`. It should be noted that the BLEU here is different from
-the BLEU calculated in prediction, and it is only for observation during
-training and evaluation.
-
-## Rouge
-### rouge-l
-
-## dureader
-## chunk
-## squad
+目前paddlenlp提供以下评价指标：
+
+| Metric                                                     | 简介                                                         | API                                                          |
+| ---------------------------------------------------------- | :----------------------------------------------------------- | ------------------------------------------------------------ |
+| Perplexity                                                 | 困惑度，常用来衡量语言模型优劣，也可用于机器翻译、文本生成等任务。 | paddlenlp.metrics.Perplexity                                 |
+| BLEU(bilingual evaluation understudy)                      | 机器翻译常用评价指标                                         | paddlenlp.metrics.BLEU                                       |
+| Rouge-L(Recall-Oriented Understudy for Gisting Evaluation) | 评估自动文摘以及机器翻译的指标                               | paddlenlp.metrics.RougeL                                     |
+| AccuracyAndF1                                              | 准确率及F1-score，可用于GLUE中的MRPC 和QQP任务               | paddlenlp.metrics.AccuracyAndF1                              |
+| PearsonAndSpearman                                         | 皮尔森相关性系数和斯皮尔曼相关系数。可用于GLUE中的STS-B任务  | paddlenlp.metrics.PearsonAndSpearman                         |
+| Mcc(Matthews correlation coefficient)                      | 马修斯相关系数，用以测量二分类的分类性能的指标。可用于GLUE中的CoLA任务 | paddlenlp.metrics.Mcc                                        |
+| ChunkEvaluator                                             | 计算了块检测的精确率、召回率和F1-score。常用于序列标记任务，如命名实体识别（NER） | paddlenlp.metrics.ChunkEvaluator                             |
+| Squad                                                      | 用于SQuAD和DuReader-robust的评价指标                         | paddlenlp.metrics.compute_predictions paddlenlp.metrics.squad_evaluate |