[llvm] [libsycl] Add Maintainers.rst file (PR #168550)

[Aaron Ballman via llvm-commits]

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@@ -511,6 +511,8 @@ Some subprojects maintain their own list of per-component maintainers.
 
 [libclc maintainers](https://github.com/llvm/llvm-project/blob/main/libclc/Maintainers.md)
 
+[libsycl maintainers](https://github.com/llvm/llvm-project/blob/main/libsycl/Maintainers.rst)
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AaronBallman wrote:

Either one is fine, it just depends on what the project prefers. In Clang, we use .rst mostly because almost all of our docs are in .rst and none are in .md, not because we dislike .md for some reason.

https://github.com/llvm/llvm-project/pull/168550