Add usage metrics and pitch to the website

[oruebel]

It would be nice to update the main landing page to:

• highlight more the different metrics. E.g., "Join a community of more than 150 labs, 400+ open datasets ....."
• include a pitch about AI, e.g., "NWB is fundamental for aggregating neurophysiology datasets for training AI models"

It would also be useful to create a new "Community Metrics" page with more detailed statistics:

• Plot of the NWB code size (with link to the NWB project analytics)
• Plot of the download of NWB data over time from the DANDI archive (with link to the DANDI statistics page)
• Plots of number of attendees at NWB events etc.
• Plots for number of data reuse publications (with link to the list of pubs)