create HF-spaces demo for Trackers (#249)

* add code for hf-spaces demo

* add examples

* disable cache

* run_on_click, move things around

* fix

* pin gradio <6.4.0, update example defaults, remove ffmpeg re-encode

* add visualization checkboxes and more examples

* add class filtering

* add link placeholders

* redesign demo UI with accordion layout, class filtering, visualization flags, and cached examples

* fix(pre_commit): 🎨 auto format pre-commit hooks

* update demo metadata, pass class names directly, swap jet trajectories, add vehicles example

---------

Co-authored-by: Piotr Skalski <piotr.skalski92@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

demo/README.md

@@ -0,0 +1,12 @@
+---
+title: Roboflow Trackers
+emoji: 🔥
+colorFrom: purple
+colorTo: green
+sdk: gradio
+sdk_version: 6.3.0
+app_file: app.py
+suggested_hardware: l4x1
+license: apache-2.0
+python_version: '3.11'
+---