update README for TA to debug

README.md

+# 重现问题
+
+- 构建`cminusfc`
+
+- ```
+  $ # at path `2022fall-compiler_cminus` 
+  $ cd tests/3-ir-gen/testcases/lv3/
+  $ cminusfc complex4.cminus
+  terminate called after throwing an instance of 'std::out_of_range'
+    what():  basic_string::erase: __pos (which is 18446744073709551615) > this->size() (which is 8)
+  [1]    22357 IOT instruction (core dumped)  cminusfc complex4.cminus
+  ```
+
+- 
+
 # 实验说明
 
 请 fork 此 repo 到自己的仓库下，随后在自己的仓库中完成实验，请确保自己的 repo 为 Private。
@@ -5,13 +20,16 @@
 ## 目前已布置的实验
 
 * [lab1](./Documentations/1-parser/)
-  + DDL：2022-10-03 23:59:59 (UTC+8)
   
+    + DDL：2022-10-03 23:59:59 (UTC+8)
+
 * [lab2](./Documentations/2-ir-gen-warmup/)
-  + DDL：2022-10-23 23:59:59 (UTC+8)
+  
+    + DDL：2022-10-23 23:59:59 (UTC+8)
 
 * [lab3](./Documentations/3-ir-gen/)
-  + DDL：2022-11-07 23:59:59 (UTC+8)
+  
+    + DDL：2022-11-07 23:59:59 (UTC+8)
 
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