[Update] Add SP2021 public access information for CS61B (#788)

- Add SP2021 course website link
  - Add Gradescope course code MB7ZPY for public access
  - Update both Chinese and English versions

Author: PangYuanbo

docs/数据结构与算法/CS61B.en.md

@@ -12,6 +12,8 @@ It is the second course of UC Berkeley's CS61 series. It mainly focuses on the d
 
 I took the version for 2018 Spring. Josh Hug, the instructor, generously made the autograder open-source. You can use [gradescope](https://gradescope.com/) invitation code published on the website for free and easily test your implementation.
 
+According to the professor's latest policy, SP2021 CS61B is now open to the public. To get everything set up, go to Gradescope and select the "Add a course" button. Enter course code **MB7ZPY** to be added.
+
 All programming assignments in this course are done in Java. Students without Java experience don't have to worry. There will be detailed tutorials in the course from the configuration of IDEA to the core syntax and features of Java.
 
 The quality of homework in this class is also unparalleled. The 14 labs will allow you to implement most of the data structures mentioned in the class by yourself, and the 10 homework will allow you to use data structures and algorithms to solve practical problems.
@@ -20,7 +22,7 @@ In addition, there are 3 projects that give you the opportunity to be exposed to
 ## Resources
 ## Course Resources
 
-- Course Website: [spring2024](https://sp24.datastructur.es/), [fall2023](https://fa23.datastructur.es/), [spring2023](https://sp23.datastructur.es/), [spring2018](https://sp18.datastructur.es/)
+- Course Website: [spring2024](https://sp24.datastructur.es/), [fall2023](https://fa23.datastructur.es/), [spring2023](https://sp23.datastructur.es/), [spring2021](https://sp21.datastructur.es/), [spring2018](https://sp18.datastructur.es/)
 - Recordings: refer to the course website
 - Textbook: None
 - Assignments: Slightly different every year. In the spring semester of 2018, there are 14 Labs, 10 Homework and 3 Projects. Please refer to the course website for specific requirements.

docs/数据结构与算法/CS61B.md

@@ -13,14 +13,16 @@
 我上的是 2018 年春季学期的版本，该课的开课老师 Josh Hug 教授慷慨地将 autograder 开源了，大家可以通过网站公开的邀请码在 [gradescope](https://gradescope.com/)
  免费加入课程，从而方便地测评自己的代码。
 
+根据教授最新的政策，SP2021 的 CS61B 也对公众开放。要设置所有内容，请前往 Gradescope 并选择"Add a course"按钮。输入课程代码 **MB7ZPY** 以添加课程。
+
 这门课所有的编程作业都是使用 Java 完成的。没有 Java 基础的同学也不用担心，课程会有保姆级的教程，从 IDEA（一款主流的 Java 编程环境）的配置讲起，把 Java 的核心语法与特性事无巨细地讲授，大家完全不用担心跟不上的问题。
 
 这门课的作业质量也是绝绝子。14 个 lab 会让你自己实现课上所讲的绝大部分数据结构，10 个 Homework 会让你运用数据结构和算法解决实际问题，
 另外还有 3 个 Project 更是让你有机会接触上千行的工程代码，在实战中磨练自己的 Java 能力。
 
 ## 课程资源
 
-- 课程网站：[spring2024](https://sp24.datastructur.es/), [fall2023](https://fa23.datastructur.es/), [spring2023](https://sp23.datastructur.es/), [spring2018](https://sp18.datastructur.es/)
+- 课程网站：[spring2024](https://sp24.datastructur.es/), [fall2023](https://fa23.datastructur.es/), [spring2023](https://sp23.datastructur.es/), [spring2021](https://sp21.datastructur.es/), [spring2018](https://sp18.datastructur.es/)
 - 课程视频：原版视频参见课程网站，B站有中文翻译搬运。
 - 课程教材：无
 - 课程作业：每年略有不同，18 年春季学期有 14 个 Lab，10 个 Homework以及 3 个 Project，具体要求详见课程网站。