add readme

README.md

@@ -0,0 +1,22 @@
+## Standard
+Install
+```
+pip install numpy matplotlib plotly
+```
+Run
+```
+python main.py
+```
+Result:
+- A html with the 3d plot is saved which can be viewed in a browser
+- The xyz trajectory plot opens
+
+## If you want to use the default 3d plot instead of the html
+1. No need to install plotly
+2. (Un)comment line 26-29 in main.py
+
+Result:
+- The 3d matplotlib plot opens
+- Press q, then the xyz plot opens
+
+Questions: 12432115@zju.edu.cn or open an issue.