Update Expo docs

[umarhadi]

This pull request updates the docs/SETUP-EXPO.md file to clarify the setup process for react-native-vector-icons with Expo and provide guidance on avoiding common build issues. Key changes include marking the font config plugin setup as optional, reorganizing instructions, and adding a new section on avoiding manual font duplication.

Updates to setup instructions:

• Updated the section title to "Set up font config plugin (Optional)" and clarified that using the config plugin is optional but recommended for preloading fonts at build time.
• Simplified and reorganized the steps for adding the font config plugin to app.config.js or app.config.json.

New guidance on avoiding font duplication:

• Added a new section, "⚠️ Important: Avoid Manual Font Duplication," explaining that recent versions of react-native-vector-icons handle font bundling automatically for native platforms.
• Included a warning about potential iOS build errors caused by duplicate font copies and provided a link to a related GitHub issue for further details.
• Provided an example configuration for adding only custom fonts to the expo-font plugin, along with a caution against adding fonts from node_modules/@react-native-vector-icons/Fonts.

[vonovak]

Thanks for pointing this out.

This is good but it's conflicting a little: we say that using the config plugin is recommended, but in light of the duplication, I think we should remove that section altogether, and keep just "Avoid Manual Font Duplication" section.

Thank you!