Add Partstack to sponsors

content/sponsors/index.adoc

@@ -35,6 +35,12 @@ Many thanks to our sponsors for supporting the LibrePCB project:
   https://www.pcbgogo.com/promo/librepcb01[$25 PCB for just $1 with free shipping]
   on your first order. PCBgogo supports the LibrePCB project financially.
 
+| image:/img/sponsor-partstack.svg[link="https://partstack.com/"]
+| https://partstack.com/[Partstack] is an electronic part search engine from
+  California, providing a comprehensive catalog of parts including supplier
+  stock availability, prices, datasheets and more. They support the LibrePCB
+  project financially.
+
 | image:/img/sponsor-hdrain.png[link="https://www.hd-rain.com/"]
 | https://www.hd-rain.com/[HD Rain] from France develops satellite
   based meteorological sensors to provide high-accuracy real-time weather

layouts/_default/home.html

@@ -158,27 +158,31 @@ <h1>Sponsors</h1>
       <div class="d-flex align-items-center justify-content-center flex-column flex-md-row">
         <a href="https://nlnet.nl/project/LibrePCB/" class="m-3">
           <img src="./img/nlnet-monochrome.png" alt="nlnet.nl"
-               style="height:50px; width:auto; object-fit:contain;">
+               style="height:40px; width:auto; object-fit:contain;">
         </a>
         <a href="https://aisler.net/" class="m-3">
           <img src="./img/sponsor-aisler.png" alt="aisler.net"
-               style="height:45px; width:auto; object-fit:contain;">
+               style="height:38px; width:auto; object-fit:contain;">
         </a>
         <a href="https://www.pcbway.com" class="m-3">
           <img src="./img/sponsor-pcbway.png" alt="www.pcbway.com"
-               style="height:40px; width:auto; object-fit:contain;">
+               style="height:35px; width:auto; object-fit:contain;">
         </a>
         <a href="https://www.pcbgogo.com/promo/librepcb" class="m-3">
           <img src="./img/sponsor-pcbgogo-light.png" alt="www.pcbgogo.com"
-               style="height:40px; width:auto; object-fit:contain;">
+               style="height:35px; width:auto; object-fit:contain;">
+        </a>
+        <a href="https://partstack.com/" class="m-3">
+          <img src="./img/sponsor-partstack-light.svg" alt="partstack.com"
+               style="height:35px; width:auto; object-fit:contain;">
         </a>
         <a href="https://www.hd-rain.com/" class="m-3">
           <img src="./img/sponsor-hdrain.png" alt="hd-rain.com"
-               style="height:30px; width:auto; object-fit:contain;">
+               style="height:25px; width:auto; object-fit:contain;">
         </a>
         <a href="https://www.cloudscale.ch/" class="m-3 pb-1">
           <img src="./img/sponsor-cloudscale.png" alt="cloudscale.ch"
-               style="height:30px; width:auto; object-fit:contain;">
+               style="height:25px; width:auto; object-fit:contain;">
         </a>
       </div>
       <div class="container mt-3">