Update README.md (#643) [ci skip]

* Update README.md

Added recommendation to use an older or cheaper Pi (not a Pi 5) for a first build.

* Update README.md

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Co-authored-by: probonopd <probonopd@users.noreply.github.com>

README.md

@@ -33,7 +33,7 @@ Video about this project by [Floyd Steinberg](https://www.youtube.com/watch?v=Z3
 ## System Requirements
 
 - Raspberry Pi 1, 2, 3, 4, or 400. Raspberry Pi Zero and Zero 2 can be used but need HDMI or a supported i2s DAC for audio out. On Raspberry Pi 1 and on Raspberry Pi Zero there will be severely limited functionality (only one tone generator instead of 8)
-- Raspberry Pi 5 can be used but currently support is experimental; HDMI sound and USB Gadget mode are not available yet 
+- Raspberry Pi 5 can be used but currently support is experimental: HDMI sound and USB Gadget mode are not available yet, and it is not clear if there are implications for cooling from running MiniDexed. Also, MiniDexed is currently not taking advantage of the higher processing power of the Raspberry Pi 5 yet. *Hence, you may consider using one of the less expensive, older Raspberry Pi boards for your first build.*
 - A [PCM5102A or PCM5122 based DAC](https://github.com/probonopd/MiniDexed/wiki/Hardware#i2s-dac), HDMI display or [audio extractor](https://github.com/probonopd/MiniDexed/wiki/Hardware#hdmi-to-audio) for good sound quality. If you don't have this, you can use the headphone jack on the Raspberry Pi but on anything but the Raspberry 4 the sound quality will be seriously limited
 - Optionally (but highly recommended), an [LCDC1602 Display](https://www.berrybase.de/en/sensors-modules/displays/alphanumeric-displays/alphanumerisches-lcd-16x2-gr-252-n/gelb) (with or without i2c "backpack" board) and a [KY-040 rotary encoder](https://www.berrybase.de/en/components/passive-components/potentiometer/rotary-encoder/drehregler/rotary-encoder-mit-breakoutboard-ohne-gewinde-und-mutter)