Fix typo: missing punctuation mark

This fix adds a period at the end of the sentence.

Author: sharonytlau

src/guide/essentials/event-handling.md

@@ -331,7 +331,7 @@ For example:
 ```
 
 ::: tip
-Note that modifier keys are different from regular keys and when used with `keyup` events, they have to be pressed when the event is emitted. In other words, `keyup.ctrl` will only trigger if you release a key while holding down `ctrl`. It won't trigger if you release the `ctrl` key alone
+Note that modifier keys are different from regular keys and when used with `keyup` events, they have to be pressed when the event is emitted. In other words, `keyup.ctrl` will only trigger if you release a key while holding down `ctrl`. It won't trigger if you release the `ctrl` key alone.
 :::
 
 ### `.exact` Modifier