[NEW] Added a link to contributing.md (#12856)

* Added a link to contributing.md

fixes - #12845

* Modified link to relative

* Added link to Contributing docs

README.md

@@ -437,7 +437,7 @@ If you want to help, send an email to support at rocket.chat to be invited to th
 
 ## How to Contribute
 
-Already a JavaScript developer? Familiar with Meteor? [Pick an issue](https://github.com/RocketChat/Rocket.Chat/labels/contrib%3A%20easy), push a PR and instantly become a member of Rocket.Chat's international contributors community.
+Already a JavaScript developer? Familiar with Meteor? [Pick an issue](https://github.com/RocketChat/Rocket.Chat/labels/contrib%3A%20easy), push a PR and instantly become a member of Rocket.Chat's international contributors community. For more information, check out our [Contributing Guide](.github/CONTRIBUTING.md) and our [Official Documentation for Contributors](https://rocket.chat/docs/contributing/).
 
 A lot of work has already gone into Rocket.Chat, but we have much bigger plans for it!