Merge pull request #2428 from mattermost/it33-patch-2

Adding Mattermost mission

Author: amyblais

source/overview/index.rst

@@ -1,7 +1,9 @@
 Mattermost Overview
 -------------------
 
-Overviews of features, security, deployment, integrations and authentication.
+Mattermost's mission is to make the world safer and more productive by developing and delivering secure, open source collaboration software that is trusted, flexible and offers fast time-to-value.
+ 
+Below is an overview of our features, security, deployment, integrations, authentication approach and compliance support.
 
 .. toctree::
    :maxdepth: 2