chore: add contributing document

CONTRIBUTING.md

@@ -0,0 +1,52 @@
+# Contributing
+
+
+## Getting the source
+
+- Check out source code:
+  ```bash
+  git clone https://github.com/orientechnologies/orientdb.git orientdb
+  ```
+
+## Prerequisites
+
+A Java JDK version 8 or later is needed.  
+Maven 3.5 or later is needed.  
+
+## Build 
+
+- Only compile
+
+    ```bash
+    mvn clean compile
+    ```
+- Run base tests
+
+    ```bash
+    mvn clean test
+    ```
+- Full build
+
+    ```bash
+    mvn clean install
+    ```
+- Run integration tests (hours long tests)
+
+    ```bash
+    mvn clean install failsafe:integration-test
+    ```
+- Format the code with standard format used by OrientDB
+
+    ```bash
+    mvn com.coveo:fmt-maven-plugin:format
+    ```
+
+## Produce Community Distribution
+
+To produce the community distribution just run  
+
+```bash
+mvn clean install
+```  
+
+this will produce two files `distribution/target/orientdb-community-(version).tar.gz` `distribution/target/orientdb-community-(version).zip`