This sketch contains minor changes to the Arduino sketch that allows one to use an ESP8266 ( Wemos D1 mini in my case) as an ISP.
I used it to program ATtiny85 Wiring Wemos ATtiny85 SCK (D5) > pin 7 (SCK) MISO (D6) > pin 6 (MISO) MOSI (D7) > pin 5 (MOSI) D4 > pin 1 (RESET) GND > pin 4 3.3v > pin 8
To upload a sketch to the ATtiny85. After installing the ISP sketch, change the board type to ATtiny85.
Note this assumes you have already installed Arduino IDE support for the ATtiny85