docs: fix comment and JSDoc spelling typos

Correct "occurred" in IMouseEvent and keydown JSDoc, remove duplicate
"This" in EscapeSequenceParser ZDM comment, use "elapsed" instead of
"lapsed" in TimeBasedDebouncer, and fix "event" in Keyboard comment.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/browser/CoreBrowserTerminal.ts

@@ -102,7 +102,7 @@ export class CoreBrowserTerminal extends CoreTerminal implements ITerminal {
   private _keyDownHandled: boolean = false;
 
   /**
-   * Records whether a keydown event has occured since the last keyup event, i.e. whether a key
+   * Records whether a keydown event has occurred since the last keyup event, i.e. whether a key
    * is currently "pressed".
    */
   private _keyDownSeen: boolean = false;