Update js-interop.md

Fix: a possible spelling mistake.

docs/next/guide/js-interop.md

@@ -4,7 +4,7 @@ title: JS Interop
 
 # JS Interop
 
-Sycamore is build upon
+Sycamore is built upon
 [`wasm-bindgen`](https://rustwasm.github.io/wasm-bindgen/) which allows calling
 JS and browser APIs from Rust. This means that you can also use `wasm-bindgen`
 to call JS from Rust. However, for calling browser APIs, the `web-sys` and