I did “platformio lib install 1101” (PlatformIO Registry),
I installed this: PlatformIO Registry (follow instructions)
I did similar things to other libraries.
When I click the platformio:build button, it still complains:
fatal error: ESP8266WiFi.h: No such file or directory
fatal error: ESP8266WiFiMulti.h: No such file or directory
fatal error: ESP8266Webserver.h: No such file or directory