Update contribution guidelines

contributing.md

@@ -1,3 +1,12 @@
 # Contribution Guidelines
 
-Please sign a cla, thanks!
+- **To add, remove, change:** Edit the `README.md` and then submit a pull request.
+- Items of category should be sorted *alphabetically*.
+- Each item should be limited to one link.
+- The link should be the name of the project.
+- The link and description are separated by a dash.
+- The description starts with an uppercase character and ends with a period.
+- The description should be clear, concise, and non-promotional.
+- Consistent and correct naming. For example, `Node.js`, not `NodeJS` or `node.js`.
+
+Thanks everyone!