Add info text to spotlights page

Adds an info text about Helmholtz Spotlights.

Closes #305 (closed)

/cc @lisa.klaffki @frust45

added Progress::2_ToDo Software Spotlight Subsite labels

requested review from @jandt-desy

assigned to @jandt-desy

added Progress::4_Can review label and removed Progress::2_ToDo label

changed the description

approved this merge request

merged

mentioned in commit 15331888

mentioned in issue #305 (closed)