Update link to coding style guide (#546)

* Update link to coding style guide

* Update CONTRIBUTING.md

---------

Co-authored-by: Mateusz Front <mfront3@gmail.com>

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 Any contributions to Membrane Framework are welcome. If you would like contribute, but you're not sure how to start or have some questions, don't hesitate to contact us via channels described in [README](README.md#support-and-questions)
 
-Before subitting code please read our [Coding style guide](https://github.com/membraneframework/membrane-core/wiki/Coding-style-guide)
+Before submitting code please read our [Coding style guide](https://membrane.stream/guide/v0.9/contributing_guide.html)
 
 When contributing to existing repo:
 
@@ -14,4 +14,4 @@ When contributing to existing repo:
 
 If you wish to create a new plugin you can give us a shout and if it's something we want as a part of our ecosystem we'll create a repo for you, guide you on your work and maintain the plugin in future.
 
-However, if feel confident enough to maintain it on your own, you can, of course, create your own repo and hex package - we only ask you to follow the naming convetions of the framework package and modules. In that case, don't forget to let us know about your work so we could include it on the list of available plugins.
+However, if you feel confident enough to maintain it on your own, you can, of course, create your own repo and hex package - we only ask you to follow the naming convetions of the framework package and modules. In that case, don't forget to let us know about your work so we could include it on the list of available plugins.