Add KIT demo instances to ELN section

[jliermann]

KIT has demo instances which should be added to the ELN section:

• https://demo.chemotion.scc.kit.edu/ on /docs/40_smartlab/15_choose_eln.mdx
• https://demo.chemotion.ibcs.kit.edu/ on /docs/40_smartlab/41_chemotion_eln/10_chemotion.mdx

Thanks to @nicolejung for pointing out!