Writing documentation

[itadera]

practical usages of this package should be described in each README.md in English.

Besides, I will writing a notes like a textbook on robotics for Human-Robot Cooperation based on this package. This book will be out of my job, it is my private task so that I will write this in Japanese.

[itadera]

I have just started writing a book on basic robotics for HRC, which is under construction but already in public. 「人間機械協調のためのロボット工学」（仮題） https://itadera.github.io/robotics4hrc/