Typo fix in README.

Author: jamie-lemon

README.md

@@ -10,7 +10,7 @@ An example of [MuPDF WebViewer](https://webviewer.mupdf.com) within a React proj
 ## Before you start
 
 - Visit [https://webviewer.mupdf.com/account](https://webviewer.mupdf.com/account) to get a license key.
-- Copy the license key and replace `YOUR_LICENCE_KEY` in `src/App.jsx` with the license key.
+- Copy the license key and replace `YOUR_LICENSE_KEY` in `src/App.jsx` with the license key.
 
 > [!TIP] 
 > Ensure to register `localhost` as a domain for your license key if you require to test locally!