Update HTML visualizer

[mishig25]

Updated dataset visualizer

Already deployed at: https://huggingface.co/spaces/lerobot/visualize_dataset

1. React.js based rewrite (compared to one giant html template we had before): more performance optimized
2. easier to read/understand/contribute for me, others, llms (as lerobot format grows, so will features of the visualizer) better sync of time between charts, videos, playback bar
3. better UI both for desktop & mobile
4. maximize or hide videos
5. multiple data graphs based on range (i.e. values with similar scales are in same chart) for easier/clearer viewing of sensors/motors data

[aliberts]

Thank you @mishig25! After trying it locally with lerobot/pusht, I have a few questions/suggestions:

• Is it possible to have this app message

> next start --port=9090

   ▲ Next.js 15.3.1
   - Local:        http://localhost:9090
   - Network:      http://172.18.128.220:9090

 ✓ Starting...
 ✓ Ready in 233ms

to be displayed after having downloaded the dataset? This is for two reasons: if I open to page before download is complete, I just land on an error page. Second reason is simply that it gets buried in the terminal's output when it's downloading files.

• The left panel displaying episodes list seems to disappear after a few seconds. When pressing up or down (shortcuts to next/previous episode) it appears again for a few seconds.
• I tried to hide the video by clicking the "X" on the top right corner of it but with no effect (maximizing works though)
• Given the size of the generated files and what this could become, I'm starting to think this visualizer app could go in a separate, dedicated repo entirely (later of course). Wdyt?