Update the online communities section with newer logos

Signed-off-by: Stasia Michalska <hel@lcp.world>

Author: hellcp

source/assets/images/logos/discord.png

@@ -21,7 +21,7 @@ <h1 class="pagetitle">Online Communities</h1>
 
       <h3 style="margin-bottom: 0; margin-top: 1em;">
         <a href="{{ site.links.discord_invite }}">
-          <img src="{{ site.asset_path }}/images/logos/discord.png" height=61 />
+          <img src="{{ site.asset_path }}/images/logos/discord.svg" />
         </a>
       </h3>
       <p>
@@ -31,7 +31,7 @@ <h3 style="margin-bottom: 0; margin-top: 1em;">
 
       <h3 style="margin-bottom: 0; margin-top: 1em;">
         <a href="http://stackoverflow.com/questions/tagged/pebble-sdk">
-          <img src="{{ site.asset_path }}/images/logos/stackoverflow.png" height=40 />
+          <img src="{{ site.asset_path }}/images/logos/stackoverflow.svg" />
         </a>
       </h3>
       <p>
@@ -42,7 +42,7 @@ <h3 style="margin-bottom: 0; margin-top: 1em;">
 
       <h3 style="margin-bottom: 0; margin-top: 1em;">
         <a href="https://www.hackster.io/pebble/projects">
-          <img src="{{ site.asset_path }}/images/logos/hackster.png" height=30 />
+          <img src="{{ site.asset_path }}/images/logos/hackster.svg" />
         </a>
       </h3>
       <p>