Update README.md

update build instruction

Author: sidd-kishan

README.md

@@ -40,7 +40,7 @@ If not, compile [CMake from source](https://cmake.org/download/#latest) first.
 
 ```
 git clone --depth 1 https://github.com/sidd-kishan/PicoPiFi
-cd pico-webserver
+cd PicoPiFi
 git submodule update --init
 cd pico-sdk
 git submodule update --init