Adding the Coding Convention into contribution guide

CONTRIBUTING.md

@@ -14,15 +14,15 @@ All types of contributions are encouraged and valued. See the [Table of Contents
 <!-- omit in toc -->
 ## Table of Contents
 
-- [I Have a Question](#i-have-a-question)
-- [I Want To Contribute](#i-want-to-contribute)
-- [Reporting Bugs](#reporting-bugs)
-- [Suggesting Enhancements](#suggesting-enhancements)
-- [Your First Code Contribution](#your-first-code-contribution)
-- [Improving The Documentation](#improving-the-documentation)
-- [Styleguides](#styleguides)
-- [Commit Messages](#commit-messages)
-- [Join The Project Team](#join-the-project-team)
+    - [I Have a Question](#i-have-a-question)
+    - [I Want To Contribute](#i-want-to-contribute)
+    - [Reporting Bugs](#reporting-bugs)
+    - [Suggesting Enhancements](#suggesting-enhancements)
+    - [Your First Code Contribution](#your-first-code-contribution)
+    - [Improving The Documentation](#improving-the-documentation)
+    - [Coding Conventions](#Coding-Conventions)
+    - [Commit Messages](#commit-messages)
+    - [Join The Project Team](#join-the-project-team)
 
 
 
@@ -138,8 +138,144 @@ include Setup of env, IDE and typical getting started instructions?
 Updating, improving and correcting the documentation
 
 -->
+## Coding Conventions
+
+This is all about standardization :blush:
+
+### Folders and Files Naming
+
+All of the folders and files should use `kebab-case`.
+
+> The `kebab-case` usage (in package, folder and file names) will make us easier when it's time to extract them into itsown package in the future.
+>
+> [Here is the related discussion](https://github.com/ageddesi/Mocked-API/issues/121#issuecomment-1273622574).
+
+### File Extensions
+
+This is all about the files and the clear definition of their usage :
+
+    - APIs
+        - `*.routes.ts`
+        - This file located right inside the feature's folder
+    - Data
+        - `*.ts`
+        - This file located under `data` folder of the feature's folder (e.g. `data/*.ts`)
+        - This `data` folder is used to store the static data used in APIs (not your mock data)
+    - Interfaces/Types
+        - `*.types.ts`
+        - This file located under `models` folder of the feature's folder (e.g. `models/*.types.ts`)
+    - Utilities
+        - `*.ts`
+        - This file located under `utils` folder of the feature's folder (e.g. `utils/*.ts`)
+    - Tests
+        - `*.test.ts`
+        - This file located under `tests` folder of the feature's folder (e.g. `tests/*.test.ts`)
+        - This `tests` folder should follow the feature's folder structure, e.g. :
+            - `tests/*.test.ts` -> test file for the APIs
+            - `tests/utils/*.test.ts` -> test file for the APIs
+
+### File Structures
+
+The file structures in this repository should look like this :
+
+    Mocked-API
+    │   README.md
+    │   package.json
+    │   ...
+    │
+    └───middleware
+    │   │
+    │   └───rate-limiter
+    │       │   rate-limiter.ts
+    │       │
+    │       └───models
+    │           │
+    │           └───rate-limiter-response.ts
+    │
+    └───modules
+    │   │
+    │   └───feature-sample-1
+    │   │   │   feature-sample-1.routes.ts
+    │   │   │
+    │   │   └───data
+    │   │   │   │   data-1.ts
+    │   │   │   │   data-2.ts
+    │   │   │   │   ...
+    │   │   │
+    │   │   └───models
+    │   │   │   │   address.types.ts
+    │   │   │   │   country.types.ts
+    │   │   │   │   ...
+    │   │   │
+    │   │   └───utils
+    │   │   │   │   util-1.ts
+    │   │   │   │   util-2.ts
+    │   │   │   │   ...
+    │   │   │
+    │   │   └───tests   /* Should have the same structure with `feature-sample-1` folder */
+    │   │       │   feature-sample-1.test.ts   /* Test for `feature-sample-1.routes.ts` */
+    │   │       │
+    │   │       └───utils
+    │   │           │   util-1.test.ts
+    │   │           │   util-2.test.ts
+    │   │           │   ...
+    │   │
+    │   └───feature-sample-2
+    │   │   │   *.routes.ts
+    │   │   │
+    │   │   └───data
+    │   │   │   │
+    │   │   │   └─── *.ts
+    │   │   │
+    │   │   └───models
+    │   │   │   │
+    │   │   │   └─── *.types.ts
+    │   │   │
+    │   │   └───utils
+    │   │   │   │
+    │   │   │   └─── *.ts
+    │   │   │
+    │   │   └───tests   /* Should have the same structure with `feature-sample-2` folder */
+    │   │       │   *.test.ts
+    │   │       │
+    │   │       └───utils
+    │   │           │
+    │   │           └─── *.ts
+    │   │
+    │   └───feature-sample-3
+    │       │   *.routes.ts
+    │       │
+    │       └───data
+    │       │   │
+    │       │   └─── *.ts
+    │       │
+    │       └───models
+    │       │   │
+    │       │   └─── *.types.ts
+    │       │
+    │       └───utils
+    │       │   │
+    │       │   └─── *.ts
+    │       │
+    │       └───tests   /* Should have the same structure with `feature-sample-3` folder */
+    │           │   *.test.ts
+    │           │
+    │           └───utils
+    │               │
+    │               └─── *.ts
+    │
+    └───utils
+    │   │   file-utils-1.ts
+    │   │   file-utils-2.ts
+    │   │   ...
+    │   │
+    │   └───tests
+    │       │   file-utils-1.test.ts
+    │       │   file-utils-2.test.ts
+    │       │   ...
+    │
+    └───another-folders
 
-## Styleguides
 ### Commit Messages
 <!-- TODO