Adds Merge Request template for Spotlights

- adds the template
- updates CONTRIBUTING.md

Closes #315

.gitlab/merge_request_templates/add_new_software_spotlight.md

+<!--
+This is the issue template for adding new Software Spotlights.
+
+Notes
+-----
+* please do not alter the assignments and labels.
+* please add only one spotlight per merge request.
+
+If you are looking for instructions how to add a software spotlight, please visit https://hifis.net/CONTRIBUTING.html#adding-software-spotlights
+
+
+Note about the preview app
+--------------------------
+Please provide us a direct link to the spotlight in the preview app. This reduces the effort for all reviewers. A template is found below.Please replace BRANCH_NAME with the name of the branch you are merging from, and <SLUG> with the slug of your spotlight. Alternatively, wait until the pipeline finished building the preview, and copy-paste the link here.
+
+Credentials for preview app
+---------------------------
+
+The credentials for the preview app are (they are publicly available, so feel free to share them with your stakeholders):
+
+User: hifis
+Password: HIFISReview!
+-->
+
+<!-- Delete this line and tell us about the spotlight -->
+
+* :point_right: **[Review link](https://hifis-review-app.hzdr.de/review-apps/hifis-overall-hifis-net/<BRANCH_NAME>/spotlights/<SLUG>)**
+
+#### Checklist for authors
+
+* [ ] Add a link pointing to the review app
+
+#### Checklist for reviewers
+
+* [ ] License is named by SPDX identifier
+* [ ] All links are pointing to the right place
+
+/cc @frust45 @konrad @jandt-desy
+/assign_reviewer @christian.meessen
+/label ~"Software Spotlight"
+/label ~"Progress::4_Can review" 

CONTRIBUTING.md

@@ -315,6 +315,8 @@ content:
 
 ### Workflow
 
+Before you start, please make sure to add only one Spotlight per Merge Request.
+
 1. If you are not a member of the [hifis.net repository](https://gitlab.hzdr.de/hifis/overall/hifis.net), create a fork of it in your own space.
 2. Clone the repository to your local computer and follow the instructions
    in the [README.md](https://gitlab.hzdr.de/hifis/overall/hifis.net/-/blob/master/README.md)
@@ -342,5 +344,4 @@ content:
    | Any image in the paragraph | `/assets/img/spotlights/<name_of_spotlight>/` |
 
 10. Push your changes to GitLab (either your repo, or a [branch in hifis.net](https://gitlab.hzdr.de/hifis/overall/hifis.net)).
-11. Create a Merge Request and mention @frust45, @konrad, @christian.meessen and
-   @jandt-desy.
+11. Create a new Merge Request. Below the title of the merge request, you will see a drop down list title "Description". Please choose `add_software_spotlight` as a template. The text field below will fill with some text and instructions that will help you creating the merge request.