update resources/webinars section - speaker profiles

add content to speaker sections of all webinar pages,

research speaker and put brief explanation of

- who they are,
- what they do, and
- why its relevant to their presentation on the webinar

Start in the resources/webinars section and review every webinar page's speaker section. Research each speaker, then add a brief account of who they are, what they do, and why their work relates to the presentation; done means all webinar pages have this context.

索引モデルが issue の本文から書いたものです。