remove contributing guidelines duplicate

link to `.github/CONTRIBUTING.md`

Author: adamperkowski

.github/mkdocs.yml

@@ -6,7 +6,7 @@ nav:
   - Introduction: 'index.md'
   - User Guide: 'userguide.md'
   - Contributing:
-      - Contributing Guide: 'contribute.md'
+      - Contributing Guide: '../.github/CONTRIBUTING.md'
       - Roadmap: 'roadmap.md'
   - Documentation:
       - Known Issues: 'KnownIssues.md'
@@ -86,4 +86,4 @@ plugins:
       minify_html: true
       htmlmin_opts:
           remove_comments: true
-      cache_safe: true
+      cache_safe: true