Add links to the "Introduction to Clang for Clad contributors" doc

This commit updates the contributing guidelines and the developers
documentation to have link to the newly created doc for beginner
contributors.

CONTRIBUTING.md

@@ -69,4 +69,9 @@ review quickly and successfully share several common traits:
 ### Developer Documentation
 
 We have documented several useful hints that usually help when addressing issues
-as they come during developement time in our [developer documentation](https://clad.readthedocs.io/en/latest/user/DevelopersDocumentation.html).
+as they come during developement time in our [developer documentation](https://clad.readthedocs.io/en/latest/user/DevelopersDocumentation.html). 
+
+In case you are interested in seeing the big picture and are just getting 
+started with Clang, there is a document that might interest you: [Introduction to Clang for Clad contributors](https://docs.google.com/document/d/1Dw4BLlWODmR3ohiu_ezswzuJNFQwAA8FRU3WNnvdBrQ/edit?usp=sharing). 
+It covers most of the basic concepts in Clang that Clad uses and describes the operation
+of the latter with examples for newcomers specifically.

docs/userDocs/source/user/DevelopersDocumentation.rst

@@ -126,6 +126,11 @@ to understand for the new developers.
 Internal documentation can be visited 
 `here </en/latest/internalDocs/html/index.html>`_
 
+In case you are interested in seeing the big picture and are just getting 
+started with Clang, there is a document that might interest you:
+`Introduction to Clang for Clad contributors <https://docs.google.com/document/d/1Dw4BLlWODmR3ohiu_ezswzuJNFQwAA8FRU3WNnvdBrQ/edit?usp=sharing>`__. It covers 
+most of the basic concepts in Clang that Clad uses and describes the operation
+of the latter with examples for newcomers specifically.
 Clad's Tests
 ============