Update CONTRIBUTION.md

CONTRIBUTION.md

@@ -2,3 +2,31 @@
 
 You can contribute to the library functionality by forking the project, cloning your fork to your own local machine, and push your changes to your fork, and finally, creating a pull request back to the main repository.
 
+
+
+## Standalone project / Fork
+
+The code can be cloned and tested as needed from the source code.
+
+Clone the forked repository and go into directory
+```sh
+git clone https://github.com/jensstigaard/node-vmix.git
+cd node-vmix
+```
+
+### Install dependencies (first time)
+
+```sh
+npm install # or 'yarn'
+```
+
+Compile TypeScript source code to JavaScript
+
+```sh
+npm run build # or 'yarn build'
+```
+
+Run tests
+```sh
+npm test # or 'yarn test'
+```