add debounce to Dropdown #897

Job	Run time
Build Dash Package	3m 6s
Detect Relevant Path Changes	5s
Typing Tests	2m 53s
Table Unit/Lint Tests (Python ${{ matrix.python-version }})	-1s
Table Server Tests (Group ${{ matrix.test-group }})	-1s
Run Background & Async Callback Tests (Python ${{ matrix.python-version }})	-1s
	6m 1s

Provide feedback