Update README.md

Author: mattnite

README.md

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 # Foundation libc
 
+This repo has been archived and moved to: https://github.com/ZigEmbeddedGroup/microzig/tree/main/modules/foundation-libc
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 [![Continuous Integration](https://github.com/ZigEmbeddedGroup/foundation-libc/actions/workflows/build.yml/badge.svg?branch=main)](https://github.com/ZigEmbeddedGroup/foundation-libc/actions/workflows/build.yml)
 
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 A C standard library that only implements a subset of functions that can be safely used without an operating system.
 This is called a [freestanding environment](https://en.cppreference.com/w/cpp/freestanding).