docs: add NixOS section to docs/guides/supported-systems.md (#910)

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Co-authored-by: hasezoey <[email protected]>

Author: danielpza

docs/guides/supported-systems.md

@@ -168,3 +168,9 @@ Because Gentoo dosnt base on debian, there is no specific debian version associa
 <span class="badge badge--danger">Unsupported</span>
 
 There are no official mongodb builds alpine, though there are some unoffical build of mongodb build for it which can be used
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+### NixOS
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+<span class="badge badge--danger">Unsupported</span>
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+There are no official mongodb builds for NixOS, however some users report the ubuntu binaries work with some extra configuration on NixOS, see [Issue #782](https://github.com/typegoose/mongodb-memory-server/issues/782)