feat: Add presentation templates gallery

[Ashvin-KS]

Problem

Users start from scratch every time they create a presentation.

Proposed Solution

Add a templates gallery:

• Pre-built presentation templates
• Categories (business, education, creative)
• One-click use with customization

Benefits

• Faster presentation creation
• Professional-looking outputs

[sanudking]

Hey! This looks like a great issue to work on. I'm a first-year CSE student at NIT Jalandhar participating in GSSoC 2026. I have knowledge in Typescript and would like to take this up. Can I get assigned? I'll submit a PR within a day or two. 🙏

[aaniya22]

pls assign this to me under gssoc

[Ashvin-KS]

Hey @sanudking, thanks for the detailed write-up! The implementation is fairly self-contained — it's a single .editorconfig file at the repo root. Happy to hand it off if a maintainer assigns you; otherwise I'd planned to take it forward. @Muneerali199, your call on assignment.