Add FAQ/docs about issues with IDE terminals

[TomJGooding]

The issue of Textual apps not working as expected in embedded IDE terminals (or Jupyter) seems to come up quite often, most recently #3995 and #4014. Perhaps this should at least be added as a FAQ, or the docs should be more explicit that Textual is designed to work in a proper terminal emulator.

[KRRT7]

there is a mention in the getting started link: https://textual.textualize.io/getting_started/#linux-all-distros
granted, it doesn't say it's designed to work in a proper terminal emulator, but may that part should be clarified?

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[TomJGooding]

I'm not sure why I closed this. Something in the docs or FAQ I still think would be useful, even if the folks who try to run TUIs in VSCode probably won't think to mention how they're running it.