Edited readme

Author: N-Holzschuch

README.md

@@ -1,2 +1,15 @@
 # a-Shell-commands
 shell commands, pre-compiled to webAssembly, ready to use in a-Shell
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+## Purpose
+
+[a-Shell](https://github.com/holzschu/a-shell) is a terminal for iOS. Several commands are provided, pre-compiled to iOS format. With the latest release (1.4.x), you can also execute commands compiled to webAssemly (wasm). If the command creates, writes or reads local files, it is best to use the specific [WASK-sdk](https://github.com/holzschu/wasi-sdk). 
+
+Once compiled to webAssembly, binaries can be shared with other users of a-Shell.
+
+- ctags:  https://github.com/universal-ctags/ctags/
+- file: https://github.com/file/file/
+- tree: http://mama.indstate.edu/users/ice/tree/
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+
+