docs: add cross-complilation guidelines for raspberry pi

Author: mohammadrajabraza

actix_hello_world/RaspberryPi_Deployment.md

@@ -0,0 +1,80 @@
+# Introduction
+
+This document will explain how to build and deploy Rust application for a RasperryPi (ARM architecture)
+
+<br/>
+
+# Steps
+## 1. Creating a Rust app (we laready hae one so we skip this step)
+## 2. Craeting a deployment script
+## 3. Cross-compiling the application
+
+<br/>
+
+# Creating a Rust Application
+Since we already have one so we're skipping this step
+
+<br/>
+
+# Creating a deployment script
+Since, it's a multistep process, and we'll be iterating over our application and each iteration involves at a minimum compiling on the development machine and running on the target board. So, it is useful to create an script with necessary commands to avoid typing multiple commands each time.
+
+We'll create a text file in the root of our project and name it after it's purpose `deploy` (without any extension).
+
+```bash
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+set -o xtrace
+
+cargo build --release
+```
+
+After that we can just run to execute file:
+```
+$ ./deploy
+```
+
+If you encounter with some execution related permissions error then make the script file executable with:
+
+```
+$ chmod +x ./deploy
+```
+Now you can run the script successfully.
+<br/>
+<br/>
+At this point we have compiled our app in release mode. We can inspect this compiled binary with the following command: 
+```
+$ file ./target/release/actix_mongo_app
+```
+- `actix_mongo_app`: is the application name
+
+which prints out something like
+```
+target/release/actix_mongo_app: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=7d6ea5fc91dcf91b45d4cc5b2a5f180206487961, for GNU/Linux 3.2.0, with debug_info, not stripped
+```
+
+If you read this carefully, you'll find out that it is a 64-bit binary for x86_64 architecture. Let's try running this on Pi and see what happens
+
+```bash
+#!/bin/bash
+
+set -o errexit
+set -o nounset
+set -o xtrace
+
+readonly [email protected]
+readonly TARGET_PATH=/home/pi/actix_mongo_app
+readonly SOURCE_PATH=./target/release/actix_mongo_app
+
+cargo build --release
+rsync ${SOURCE_PATH} ${TARGET_HOST}:${TARGET_PATH}
+ssh -t ${TARGET_HOST} ${TARGET_PATH}
+```
+
+Let me describe the elements of the above scripts before moving further
+- `pi`: Username on raspberry pi
+- `raspberrypi.local`: Hostname of raspberry pi
+- `actix_mongo_app`: Our application name
+