tweak homepage copy to make feedback more obvious

I noticed that, if you're _reading_ the beta callout it's obviously a feedback link, but it's easy to glaze over "Tell us what you think". Here, I've added the word "feedback" to make it stand out on scanning the page, while adding "Got ideas?" to keep it feeling colloquial.

src/app/HomePage.js

@@ -382,7 +382,7 @@ function FeedbackFormPitch({ isDisabled, onClick, openButtonRef }) {
         onClick={onClick}
         ref={openButtonRef}
       >
-        Tell us what you think →
+        Got ideas? Send us your feedback →
       </Box>
     </Flex>
   );