Git clients

@laurent.heirendt Can you please check if all the technical things are ok?

Closes https://git-r3lab.uni.lu/R3-core/howto-cards-internal/issues/7.

external/git-clients/git-clients.md

+---
+layout: page
+permalink: /external/git-clients/
+---
+
+# Git clients
+
+## Installation of Git
+
+You can find installers for Windows, MacOS and Linux on the [Git webpage](https://git-scm.com/downloads).
+
+## GUI clients
+
+Here is a list of suggested Git GUI clients:
+
+* [Sourcetree](https://www.sourcetreeapp.com)
+* [Fork](https://git-fork.com)
+* [SmartGit](https://www.syntevo.com/smartgit/)
+
+You can find more clients on the [Git webpage](https://git-scm.com/downloads/guis).
+
+## IDEs
+
+There are also several IDEs (integrated development environments) that have git functionalities included:
+
+* [GitLab WebIDE](https://docs.gitlab.com/ee/user/project/web_ide/)
+* [Visual Studio Code](https://code.visualstudio.com/)
+* [Atom](https://atom.io/)
+* [IntelliJ](https://www.jetbrains.com/idea/)
+* [PyCharm](https://www.jetbrains.com/pycharm/)