Updated module descriptions

Author: fzhinkin

core/Module.md

@@ -79,15 +79,6 @@ fun Message.Companion.fromBson(source: Source): Message {
 
 Core IO primitives.
 
-# Package kotlinx.io.files
-
-Basic API for working with files.
-
 #### Thread-safety guarantees
 
 Until stated otherwise, types and functions provided by the library are not thread safe.
-
-#### Known issues
-
-- [#312](https://github.com/Kotlin/kotlinx-io/issues/312) For `wasmWasi` target, directory listing ([kotlinx.io.files.FileSystem.list]) does not work with NodeJS runtime on Windows,
-as `fd_readdir` function is [not implemented there](https://github.com/nodejs/node/blob/6f4d6011ea1b448cf21f5d363c44e4a4c56ca34c/deps/uvwasi/src/uvwasi.c#L19).

filesystem/Module.md

@@ -0,0 +1,19 @@
+# Module kotlinx-io-filesystem
+
+The module provides experimental files and filesystem support. The API is unstable and will change in the future.
+
+# Package kotlinx.io.files
+
+Basic API for working with files.
+
+#### Thread-safety guarantees
+
+Until stated otherwise, types and functions provided by the library are not thread safe.
+
+#### Known issues
+
+[//]: <> (TODO: Link to SystemFileSystem doesn't work)
+- For JS and Wasm, [kotlinx.io.files.SystemFileSystem] is supported only in the NodeJs environment. Attempts to use it
+in the browser environment will result in a runtime error.
+- [#312](https://github.com/Kotlin/kotlinx-io/issues/312) For `wasmWasi` target, directory listing ([kotlinx.io.files.FileSystem.list]) does not work with NodeJS runtime on Windows,
+as `fd_readdir` function is [not implemented there](https://github.com/nodejs/node/blob/6f4d6011ea1b448cf21f5d363c44e4a4c56ca34c/deps/uvwasi/src/uvwasi.c#L19).