Update README.md

Update README.md and include some minimal information about this
crate.

Signed-off-by: Sergio Lopez <slp@redhat.com>

Author: slp

README.md

@@ -1,41 +1,14 @@
-# Crate Name
+# vhost-user-backend
 
 ## Design
 
-TODO: This section should have a high-level design of the crate.
+This crate provides convenient abstractions for implementing `vhost-user` device server backends:
 
-Some questions that might help in writing this section:
-- What is the purpose of this crate?
-- What are the main components of the crate? How do they interact which each
-  other?
+- A vhost-user backend trait (`VhostUserBackend`)
+- A public API for the backend to interact with (`VhostUserDaemon`)
+- An structure including virtio queue related elements (`Vring`)
+- A worker for receiving queue events and forwarding them to the backend.
 
 ## Usage
 
-TODO: This section describes how the crate is used.
-
-Some questions that might help in writing this section:
-- What traits do users need to implement?
-- Does the crate have any default/optional features? What is each feature
-  doing?
-- Is this crate used by other rust-vmm components? If yes, how?
-
-## Examples
-
-TODO: Usage examples.
-
-```rust
-use my_crate;
-
-...
-```
-
-## License
-
-**!!!NOTICE**: The BSD-3-Clause license is not included in this template.
-The license needs to be manually added because the text of the license file
-also includes the copyright. The copyright can be different for different
-crates. If the crate contains code from CrosVM, the crate must add the
-CrosVM copyright which can be found
-[here](https://chromium.googlesource.com/chromiumos/platform/crosvm/+/master/LICENSE).
-For crates developed from scratch, the copyright is different and depends on
-the contributors.
+Users of this create are expected to implement the `VhostUserBackend` trait and to initialize the execution context by instantiating `VhostUserDaemon` and calling to its `start` method.