add cmake install as part of setting up executorch

Summary: cmake may not be installed in some machines

Reviewed By: shoumikhin

Differential Revision: D49195762

fbshipit-source-id: 216460b23974dbe86fccc3f686981fce75b29a0b

Author: cccclai

docs/website/docs/tutorials/00_setting_up_executorch.md

@@ -16,6 +16,7 @@ To install conda, you can look at the
 conda create -yn executorch python=3.10.0
 conda activate executorch
 
+conda install cmake
 conda install -c conda-forge flatbuffers
 ```