mark all inactive labs with new marker "inactive"

[sonjafischbauer]

a new marker was created, see #424

1) @k-nut could you drop us a hint where we can add this new marker/ label, and with which syntax?

2) @noratitz mark labs inactive where applicable. Use for reference the "Lab Übersicht.xlsx" created in 2023. (as discussed in today's call)

[k-nut]

To mark the labs as inactive, add the inactive: true line in the frontmatter of the lab like I did in this exemplary commit. That will update them on the map and show the badge on the individual lab pages.

[sonjafischbauer]

thank you so much

[sonjafischbauer]

pull request is out, closing this, done!