Add docs for contribution workflow and local development env

Added:

• documentation pages for:
  • local dev env
  • contribution workflow
  • contributing docs

.gitlab-ci.yml

@@ -444,7 +444,7 @@ latest_image:
 docs:
   interruptible: true
   image: $CI_REGISTRY_IMAGE/conda:$CI_COMMIT_REF_NAME
-  stage: sphinx-docs
+  stage: docs
   before_script: [ ]
   script:
     # install tex dependencies