docs: Add CONTRIBUTING.md

A `CONTRIBUTING.md` is considered a good practice
for open source projects. It helps developers to
get started quickly.

It clearly doesn't replace the already existing guide
for content contributors. The `CONTRIBUTING.md` is only
focused on developers.

Author: MoritzWeber0

CONTRIBUTING.md

@@ -0,0 +1,49 @@
+# Contributing
+
+Thanks for your interest in the FIP guide. Contributions are always welcome!
+
+This guide is intended for developers.
+If you just want to contribute content, you can find more information in the [Wiki](/../../wiki/English).
+
+We are committed to fostering a welcoming, respectful, and harassment-free
+environment. Be kind!
+If you have questions, ideas or want to report a bug, feel free to
+[open an issue](/../../issues). Or go ahead and
+[open a pull request](/../../pulls) to contribute code.
+
+## Getting Started
+
+### Prerequisites
+
+The project uses Hugo as framework for the website. Therefore, hugo must first be installed.
+You can find the instructions in the official [Hugo documentation](https://gohugo.io/installation/).
+
+Validate the installation by running `hugo version` in the command line.
+
+In addition, we use some node packages, for example bootstrap as UI toolkit. To install the packages,
+install the node package manager `npm` on your machine. Instructions are available in the [official documentation](https://docs.npmjs.com/downloading-and-installing-node-js-and-npm).
+
+Validate the installation by running `npm --version` in the command line.
+
+### Start the development server
+
+First of all, we have to the install the node packages by running: 
+
+```zsh
+npm i
+```
+
+Then, we can start the integrated hugo server with:
+
+
+```zsh
+hugo server
+```
+
+Check the output and follow the link to see a local preview of the changes.
+
+To initialize the search index, run the following command in a separate terminal window:
+
+```zsh
+npx -y pagefind --site public
+```