Resolve "Add software spotlights: Lynx, MeshIt, Golem"

Closes #319 (closed)

This merge request from branch #319 (closed) adds three spotlights for GFZ's softwares meshit, golem and lynx. Everything has been tested locally on a Jekyll instance.

• 👉 Review link

Checklist for authors

• Add a link pointing to the review app

Checklist for reviewers

• File size of images is not too large
• Update date_added attribute
• License is named by SPDX identifier if possible
• All links are pointing to the right place

/cc @frust45 @konrad @jandt-desy