Linkedin,Facebook links updated inReadme file of mattermost-server (#16186)

Automatic Merge

README.md

@@ -80,9 +80,11 @@ See the [LICENSE file](LICENSE.txt) for license rights and limitations.
 
 ## Get the Latest News
 
-- **Twitter** - Follow [Mattermost](https://twitter.com/mattermost)
+- **Twitter** - Follow [Mattermost](https://twitter.com/mattermost).
 - **Blog** - Get the latest updates from the [Mattermost blog](https://mattermost.com/blog/).
-- **Email** - Subscribe to our [newsletter](http://mattermost.us11.list-manage.com/subscribe?u=6cdba22349ae374e188e7ab8e&id=2add1c8034) (1 or 2 per month)
+- **Facebook** - Follow [Mattermost](https://www.facebook.com/MattermostHQ).
+- **LinkedIn** - Follow [Mattermost](https://www.linkedin.com/company/mattermost/).
+- **Email** - Subscribe to our [newsletter](http://mattermost.us11.list-manage.com/subscribe?u=6cdba22349ae374e188e7ab8e&id=2add1c8034) (1 or 2 per month).
 - **Mattermost** - Join the ~contributors channel on [the Mattermost Community Server](https://community.mattermost.com). 
 - **IRC** - Join the #matterbridge channel on [Freenode](https://freenode.net/) (thanks to [matterircd](https://github.com/42wim/matterircd)).