update: CONTRIBUTING guide to document process for adding new icons

Added instructions for adding new icons to the existing font family, including steps for using Icomoon and updating the style.css file.

Author: UnschooledGamer

CONTRIBUTING.md

@@ -166,6 +166,41 @@ refactor: simplify file loading logic
    pnpm run lang update    # Update translations
    ```
 
+## ℹ️ Adding New Icons (to the existing font family)
+> [!NOTE]
+> Acode uses SVG and converts them into a font family, to be used inside the editor and generally for plugin devs.
+> 
+> **Plugin-specific icons SHOULD NOT be added into the editor. Only generally helpful icons SHOULD BE added**
+
+Many font editing software and web-based tools exist for this purpose. Some of them are listed below.
+
+| Name | Platform |
+|------|----------|
+| https://icomoon.io/ | Free (Web-Based, PWA-supported, Offline-supported |
+| https://fontforge.org/ | Open-Source (Linux, Mac, Windows)
+
+### Steps in Icomoon to add new Icons
+
+1. Download the `icons.ttf` file from https://github.com/Acode-Foundation/Acode/tree/main/src/res/icons
+2. Go to https://icomoon.io/ > Start a new Project
+3. Import the `icons.ttf` downloaded (in step 1)
+3. All icons will be displayed after importing.
+4. Import the SVG icon created/downloaded to be added to the Font Family.
+5. On the right side, press **enable Show Characters** to view unicode character for that icon.
+6. Copy the newly added icon's Unicode character (required for later steps)
+7. Repeat Step 4 and Step 6 until all needed new icons are added.
+8. Press the export icon from the top left-hand side.
+9. Add **Font** in the formats section, expand the **Font**, enter **code-editor-icon** as the font-family for `icons.ttf` file.
+10. Press the download button, and a zip file will be downloaded.
+
+### Adding the Unicode characters to style.css.
+
+1. Open `style.css` file present at https://github.com/Acode-Foundation/Acode/tree/main/src/res/icons
+2. Add new class called `.icon.icon-name::before` i.e ```.icon.all_inclusive:before { content: "\ea18"; }```
+3. `content` (i.e `ea18` -> `\ea18`) property's value is the Unicode Character copied after importing the icon in the font family.
+4. Save the file, extract the zip file (downloaded), from the fonts folder, rename `code-editor-icon.ttf` to `icons.ttf`, copy & paste the `icons.ttf` onto https://github.com/Acode-Foundation/Acode/tree/main/src/res/icons
+5. commit the changes <ins><b>ON A NEW branch</b></ins> (by following: [Commit Messages guide](#commit-messages))
+
 ## 🔌 Plugin Development
 
 To create plugins for Acode: