update README and add LICENSE

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Chunyu
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -5,12 +5,13 @@
 愿意光临本仓库的领导们请按下面的提示参观：
 
 ```text
-.
-├── 01_TeachingDemo             # 某次上课所用实例，简要介绍功率谱估计
-├── 02_LearnDSP-MATLAB          # 数字信号处理练习：MATLAB编程
-├── 03_LearnDSP-Python          # 数字信号处理练习：Python编程
-├── figures                     # 相关图片（实际上是暂时没有归类）
-└── README.md                   # 递归的玩笑
+signal-process-demo
+    ├── 01_TeachingDemo                 # 某次课程所用的示例，简要介绍功率谱密度
+    ├── 02_LearnDSP-MATLAB              # 数字信号处理练习：MATLAB编程
+    ├── 03_LearnDSP-Python              # 数字信号处理练习：Python编程
+    ├── misc                            # 杂项
+    ├── LICENSE
+    └── README.md
 ```
 
-You may think these English sentences are the translations, which are actually not. That's a joke. Welcome to this repository to study signal process with me.
+不定时更新。