add link to github for Session messenger

Signed-off-by: Stephen L. <[email protected]>

Author: lrq3000

_includes/sections/instant-messenger.html

@@ -195,6 +195,7 @@ <h2 id="nodal" class="anchor">
   description="Encrypted instant messenger using 3-hop onion routing to transfer communications. All communications are E2EE encrypted by default, supporting 1-on-1, private group and public group chatrooms."
   website="https://getsession.org/"
   privacy-policy="https://getsession.org/privacy-policy/"
+  github="https://github.com/oxen-io/session-desktop"
   googleplay="https://play.google.com/store/apps/details?id=network.loki.messenger"
   ios="https://apps.apple.com/app/session-private-messenger/id1470168868"
   windows="https://getsession.org/windows"