added readme that describes steps for the greetings example experience (#352)

Co-authored-by: igor <dev@igor.sh>

marine-examples/greeting/README.md

@@ -0,0 +1,69 @@
+# Greeting
+
+## Overview
+
+This is a very simple service comprised of a single Wasm module, where the module only has one function, greeting. Fundamentally, this example illustrates how to build a function as a service (FaaS) for peer-to-peer deployment, with the exciting purpose of providing a hello world experience.
+
+## Build
+
+To build the example, please run the following command:
+
+```
+./build.sh
+```
+
+After the build is done, you get the module in the `artifacts` directory:
+
+```
+➜  greeting git:(main) ✗ ls artifacts
+greeting.wasm
+```
+
+## Run
+
+Test and inspect the example locally using the `mrepl` tool:
+
+```
+  greeting git:(main) mrepl Config.toml
+Welcome to the Marine REPL (version 0.16.1)
+Minimal supported versions
+  sdk: 0.6.0
+  interface-types: 0.20.0
+
+app service was created with service id = 05251276-81fe-4dad-aea1-f35981077ec1
+elapsed time 99.394571ms
+
+1> i
+Loaded modules interface:
+
+greeting:
+  fn greeting(name: string) -> string
+
+2> call greeting greeting ["Mundo"]
+result: String("Hi, Mundo")
+ elapsed time: 123.176µs
+
+3> q
+➜  greeting git:(main)
+```
+
+Alternatively we can use `cargo test`:
+
+```
+➜  greeting git:(main) cargo +nightly test --release
+ 
+ ....
+
+    Finished release [optimized] target(s) in 10m 35s
+     Running unittests src/main.rs (target/release/deps/greeting-35ba77ac6c6613e5)
+
+running 2 tests
+test tests::non_empty_string ... ok
+test tests::empty_string ... ok
+
+test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.14s
+
+➜  greeting git:(main)
+```
+
+For more detailed and in depth reading on the example please refer to the [Marine Examples Readme](../README.md#greeting-example)