Added platforms (partially) operated and documented externally (#142)

Author: naevtamarkus

docs/alps/platforms.md

@@ -5,6 +5,8 @@ A platform represents a set of scientific services along with compute and data r
 Each platform addresses particular research needs and domains, such as climate and weather modeling, machine learning, or high-performance computing applications.
 A platform can consist of one or multiple [clusters][ref-alps-clusters], and its services can be managed either by CSCS or by the scientific community itself, including access control, usage policies, and support.
 
+The following platforms are fully operated by CSCS:
+
 <div class="grid cards" markdown>
 
 -   :fontawesome-solid-mountain: __HPC Platform__
@@ -26,3 +28,31 @@ A platform can consist of one or multiple [clusters][ref-alps-clusters], and its
     [:octicons-arrow-right-24: CWP][ref-platform-cwp]
 
 </div>
+
+The following platforms are jointly operated by different Swiss projects and institutes and CSCS. Software and policies are tailored depending on the use case, and are documented separately.
+
+
+<div class="grid cards" markdown>
+
+-   :fontawesome-solid-mountain: __Merlin 7__
+
+    The Merlin resources are available to all PSI staff and external collaborators.
+
+    [:octicons-arrow-right-24: Merlin](https://www.psi.ch/en/awi/the-merlin-hpc-cluster)
+
+-   :fontawesome-solid-mountain: __Materials Cloud__
+
+    Materials Cloud is built to enable the seamless sharing and dissemination of resources in computational materials science.
+
+    [:octicons-arrow-right-24: Materials Cloud](https://www.materialscloud.org/)
+
+-   :fontawesome-solid-mountain: __Numerical weather forecasting__
+
+    MeteoSwiss uses a numerical weather forecasting model for the production of regional and local forecast products in the Alpine region.
+
+    [:octicons-arrow-right-24: NWP](https://www.meteoswiss.admin.ch/weather/warning-and-forecasting-systems/icon-forecasting-systems.html)
+
+</div>
+
+!!! under-construction
+    Add the WLCG, CTA and SKA platforms in here as well, with their respective external links.