Added Template for Preview Images

Contribution/Contribution.ipynb

@@ -78,6 +78,7 @@
     "author: \"Your full name\"\n",
     "date: \"yyyy-mm-dd\"\n",
     "categories: [code]\n",
+    "image: \"Preview_Image.png\"\n",
     "image-width: \"1cm\"\n",
     "image-height: \"1cm\"\n",
     "format:\n",
@@ -102,6 +103,8 @@
     "6. Push the changes to your github account.\n",
     "7. Log into github and create a pull request to the main github repository. The pull request should be directed to the devel branch (but we can also change that afterwards).\n",
     "\n",
+    "If you would like to include a preview image with your contribution, feel free to use our preview image template. It is available as a .png file (for non-macOS users) and a Keynote file (for macOS users). You can find the template in the main folder alongside the other files.\n",
+    "\n",
     "If you plan to introduce major changes to the base library it can be beneficial to contact us first. This way we might be able to avoid conflicts before they arise.\n",
     "\n",
     "If you used tequila for your research, feel free to include your algorithms here, either by integrating it into the core libraries or by demonstrating it with a notebook in the tutorials section. If you let us know about it, we will also add your research article in the list of research projects that use tequila (see the github repos README)."