Why are these changes needed?

• n all the notebooks/example pages where pip install ag2... is used, add a note that "if you have been using autogen or pyautogen, all you need is to upgrade it pip install -U autogen... or pip install -U pyautogen as pyautogen, autogen and ag2 are aliases for the same pypi package.
• Add missing playwright installation command for linux
• Add note that browser-use requires python >= 3.11

Related issue number

Closes #747

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.