doc: fix npm/npx mixup in oxlint-tsgolint installation (#548)

`npx add` does not exist, and should be `npm add`, just like it is documented for the base installation `npm add -D oxlint`.

Signed-off-by: Adrian Jost <[email protected]>

Author: adrianjost

src/docs/guide/usage/linter/type-aware.md

@@ -7,7 +7,7 @@ Read our [technical preview announcement](/blog/2025-08-17-oxlint-type-aware) fo
 ::: code-group
 
 ```sh [npm]
-npx add -D oxlint-tsgolint@latest
+npm add -D oxlint-tsgolint@latest
 ```
 
 ```sh [pnpm]