revert contirbuting guide, fix Dec2Bin grammar

CONTRIBUTING.md

@@ -1 +1,10 @@
-- [Viraj Sharma](https://github.com/virajsharma2000)
+## Contribution Guide
+
+This guide will help us ensure that you have a simple and effective way to contribute to this project.
+
+-   If you want to propose a new App Idea, please use the [Example Guide](./Example%20Guide.md) as a base template.
+-   Before creating a Pull Request, please make sure that your suggestion is not already added to the project. You can submit an update if you believe it improves an existing idea.
+-   Make sure you check your spelling and grammar.
+-   Create individual PR for each suggestion.
+
+Thank you for spending your time to improve this project! ^\_^

Projects/1-Beginner/Dec2Bin.md

@@ -0,0 +1,13 @@
+## User Stories
+
+-   [ ] User can enter any integer except
+-   [ ] User must be notified if 0 or 1 was entered using validation error. 
+-   [ ] User views the results in a single output field containing the binary (base 2) equivalent of the decimal that was entered
+
+@@ -34,7 +34,7 @@ constraints:
+[Binary number system](https://en.wikipedia.org/wiki/Binary_number)
+
+## Example projects
+- [decimal to binary program geeks for geeks] (https://www.geeksforgeeks.org/dsa/program-decimal-binary-conversion/)
+
+# HAPPY CODING!!