Update and rename executive-director.md to staff.md

[sandragesing]

Added a staff page with Sophia and me

Description

Checklist:

• [x] I have previewed changes locally or with CircleCI (runs when PR is created)
• [x] I have completed any content reviews, such as getting input from relevant working groups. If no, please note this and wait to post the PR to the #website channel until the content has been settled.

When you are ready for a technical review/merge, post the for the link for the PR in the US-RSE Slack (#website) to ask for reviewers.

[mrmundt]

You may also want to create a redirect: https://github.com/USRSE/usrse.github.io/tree/main/pages/redirects

[sandragesing]

There are a few other places in the tree that refer to about/executive-director:

$ grep -r "about/executive-director"  *
_data/menus/about.yml:      link: /about/executive-director
_data/navigation.yml:      link: about/executive-director/
pages/about/executive-director.md:permalink: /about/executive-director/

Do you want to update those as well?

Thanks - I updated those.

[sandragesing]

You may also want to create a redirect: https://github.com/USRSE/usrse.github.io/tree/main/pages/redirects

Thanks - I added that!