This library is based on pschatzmann/arduino-audio-tools and changed according to Seeed Studio reSpeaker Lite, and is now officially available for Arduino. The supported esp-arduino is 3.0.x or higher.
For more detailed tutorials and introductions to reSpeaker Lite read the Seeed Studio Wiki.
You can download the library as zip and call include Library -> zip library. Or you can git clone this project into the Arduino libraries folder e.g. with
cd ~/Documents/Arduino/libraries
git clone https://github.com/limengdu/reSpeaker_Lite-Arduino-Library.git
I recommend to use git because you can easily update to the latest version just by executing the git pull
command in the project folder.