docs(contrib): added contribution guidelines

Author: ghimiresdp

CONTRIBUTION.md

@@ -1 +1,35 @@
-# Instructions for contributors
+# Instruction for contributors
+
+> **Note**: _The project strictly uses `poetry` package manager so do not push
+> any `requirements.txt` file or other package management files._
+
+Rules to contribute to projects:
+
+- The main goal of this project is to unify payment process so we must inherit
+  abstract classes for creating a new payment method.
+
+- Do not use highly offensive or racist words anywhere including variable names,
+  examples, and requirement specification.
+
+- The solution should be capable of running on all operating systems.
+  If not, mention in the respective section in documentation
+
+
+## Placeholders
+Placeholders are not strict and we may use any name for them, but please try to
+name them so that everyone who understands English can understand them properly.
+
+We may use name of fictional characters of Sci-fi movies too
+but we should make sure that those names should not impact sentiments of people
+of any region, race, or gender.
+
+Examples of some placeholders:
+
+1. **Person**: `John Doe` `Darth Vader`, `Sheldon`, `Iron Man`, `Yoda`, etc.
+2. **Place**: `High Street`, `Wakanda`, `Vulkan`, `Tatooine`, etc.
+3. **Organization**: `Ace`, `Galactic Republic`, `Jedi`, `Enterprise`, ``, etc.
+4. **Domain Names** `example.com`, `starwars.com`, `johndoe.com`, etc.
+
+
+> **Note**: All of the above guidelines are created just for the reference and
+> may not be used as a proof for any legal actions.