Improve description on validation page (#693)

* Improve description on validation page

- FMU Check performs only static checks
- put fmusim more prominently

* Add link to FMPy and improve language

---------

Co-authored-by: Torsten Sommer <[email protected]>

Author: chrbertsch

content/validation.html

@@ -60,7 +60,7 @@ <h2 class="display-5 mb-3 fw-semibold lh-sm">Validate your FMUs</h2>
     <div class="row justify-content-center mb-5">
       <div class="col-xl-9">
         <h2>FMU Check</h2>
-        <p>A free web app to validate FMUs online. It's based on FMPy and hosted by the Modelica Association.</p>
+        <p>A free web app to validate FMUs online. It's based on <a href="https://github.com/CATIA-Systems/FMPy">FMPy</a>, hosted by the Modelica Association, and performs static checks only (i.e. no simulation of the FMUs).</p>
         <p class="d-flex justify-content-start lead fw-normal">
           <a href="https://fmu-check.herokuapp.com/" class="icon-link icon-link-hover fw-semibold">
             Validate your FMU <i class="fa-solid fa-arrow-right ms-1"></i>
@@ -89,7 +89,7 @@ <h2>FMPy</h2>
 
     <div class="row justify-content-center mb-5">
       <div class="col-xl-9">
-        <h2>Reference FMUs</h2>
+        <h2>Reference FMUs and fmusim</h2>
         <p>The Reference FMUs are a set of test models and the `fmusim` application to simulate FMUs. It supports</p>
         <ul>
           <li>validation of the modelDescription.xml against the XML schema</li>