chore: update feature list

Author: danielroe

README.md

@@ -33,6 +33,7 @@ The aim of [npmx.dev](https://npmx.dev) is to provide a better browser for the n
 - **Vulnerability warnings** – security advisories from the OSV database
 - **Download statistics** – weekly download counts with sparkline charts
 - **Install size** – total install size including dependencies
+- **Playground links** – quick access to StackBlitz, CodeSandbox, and other demo environments from READMEs
 - **Infinite search** – auto-load additional search pages as you scroll
 
 ### User & org pages
@@ -62,6 +63,7 @@ The aim of [npmx.dev](https://npmx.dev) is to provide a better browser for the n
 | JSR cross-reference            |    ❌     |    ✅    |
 | Vulnerability warnings         |    ✅     |    ✅    |
 | Download charts                |    ✅     |    ✅    |
+| Playground links               |    ❌     |    ✅    |
 | Dependents list                |    ✅     |    🚧    |
 | Package admin (access/owners)  |    ✅     |    🚧    |
 | Org/team management            |    ✅     |    🚧    |