update intro, add picture

[gisellerosetta]

Proposed Changes

• Update the homepage with some broader information for less technical users
• Add a picture (reused the one from Update basic usage example #302)
• Update contact email to ASAP

Related Issues

• Fixes Update docs homepage #301

Pre-requisites

This section may not be fully required if the branch is not merging into main.
Please indicate items that aren't necessary and why, with comments around incomplete checks.

• Version number has been incremented, according to SemVer NA
• Changelog has been updated, listing changes to this version. Use the keep a changelog format NA
• New features are tested NA
• New features are documented using the numpydoc docstring format NA
• Other relevant package documentation is updated
• For new functionality, examples are included in the docs or a feature request has
  been made for it/them. NA

[CHCRowley]

Nice clear landing page. I've checked build, readability, typos and links. Fixed a couple of typos and one broken link - ready to marge 😸