add Post Feed App in app ideas

[ldm-code]

Description:

• Build a simple social media feed using only HTML, CSS, and JavaScript (no backend).
• Users should be able to create, display, and manage posts containing images or videos with captions.
• All data must be stored locally using browser storage such as IndexedDB or similar.

📋 User Stories:

• User can create a post with an image or video and a caption

• User can view a list of posts in a feed layout

• User can delete their posts

• User data is persisted using browser storage (e.g., IndexedDB)

⭐ Bonus Features:

• User can like posts

• User can comment on posts

• User can toggle dark mode

• User can edit posts

• Posts display timestamps

Useful links and resources:

• HTML Reference - MDN
• CSS Reference - MDN
• JavaScript Reference - MDN
• DOM Manipulation - MDN
• CSS Flexbox - CSS-Tricks
• CSS Grid - CSS-Tricks
• Dark Mode - CSS-Tricks
• File API - MDN
• FileReader - MDN
• IndexedDB - MDN
• LocalStorage - MDN
• SessionStorage - MDN

[ldm-code]

Closes #1102