fix: typo

DEVELOPER.MD

@@ -123,7 +123,7 @@
   be putting it in.
 - If you can't think of a way to avoid media query(should be really rare for roomkit-react), make
   variants, and use media query from app.
-- No fixed height, width in pixels, avoid anything in pixels, rem, percet are fine.
+- No fixed height, width in pixels, avoid anything in pixels, rem, percent are fine.
 - There is almost always a better and more responsive solution using
   css properties than going for pixel based dimensions or media queries.
 - Write code which is easy to read, understand and customise not only as a whole