docs: update comment regarding project_options variable [skip ci]

Author: aminya

README.md

@@ -29,7 +29,8 @@ include(${_project_options_SOURCE_DIR}/Index.cmake)
 # Set the project name and language
 project(myproject LANGUAGES CXX)
 
-# Initialize project_options
+# Initialize project_options variable related to this project
+# This overwrites `project_options` and sets `project_warnings`
 # uncomment the options to enable them:
 project_options(
       ENABLE_CACHE
@@ -154,7 +155,8 @@ include(${_project_options_SOURCE_DIR}/src/GlobalOptions.cmake)
 # Set the project name and language
 project(myproject LANGUAGES CXX)
 
-# Initialize project_options
+# Initialize project_options variable related to this project
+# This overwrites `project_options` and sets `project_warnings`
 # uncomment the options to enable them:
 project_options(
       ENABLE_CACHE