Add Storefront Brief to newsletter

[Alexaliao001]

• Project Name: Storefront Brief
• Project URL: https://fortune-insight.onrender.com/shop/brief/index.html
• RSS: https://fortune-insight.onrender.com/shop/brief/feed.xml
• Issue 1 (sample): https://fortune-insight.onrender.com/shop/brief/issue-001-en.html
• Project Description: English weekly on iOS and indie App Store fees, ASO, and storefront ops. Free sample plus RSS; paid archive.
• Why it should be added to awesome-swift: Fits the existing Newsletter section (iOS / indie / App Store). English weekly covering App Store fees, ASO, and storefront ops for iOS indie developers. Archive, dedicated RSS 2.0, and Issue 1 sample are live.
• At least 15 stars (GitHub project) — n/a, this is a newsletter, not a GitHub library (same as other newsletter entries)
• Support Swift 5 — n/a, this is a newsletter, not a library
• Updated contents.json instead of README
• Lib is fully open sourced, written in Swift and not a wrapper over compiled lib — n/a, this is a newsletter, not a library
• Description does not say written in Swift or variant

JSON added under newsletter:

{
  "title": "Storefront Brief",
  "category": "newsletter",
  "description": "English weekly on iOS and indie App Store fees, ASO, and storefront ops. Free sample plus RSS; paid archive.",
  "homepage": "https://fortune-insight.onrender.com/shop/brief/index.html"
}