Add page to collect all tutorials available and show on services page

See merge request hifis/hifis.net!253

Make categories of posts visible on the frontpage

See merge request hifis/hifis.net!251

Fix cards arrangement on services page

See merge request hifis/hifis.net!252

Resolve "Failing pipeline after merge to master (but works after retry)"

Closes #141

See merge request hifis/hifis.net!250

Update event

See merge request hifis/hifis.net!243

This also renames the category of the diagrams post in order to be in
line with the other tutorials.

Use fontawesome icon for the HTML details element

See merge request hifis/hifis.net!249

Center events/news cards on front page

See merge request hifis/hifis.net!248

Fix typo in YAML metadata for Blog post 2021-06-02

See merge request hifis/hifis.net!247

Use Ruby 3.0 for the production builds

See merge request hifis/hifis.net!242

Create a post announcing and explaining Kroki usage

See merge request hifis/hifis.net!229

Allow failure on external link checker (scheduled)

See merge request hifis/hifis.net!241

Mod proposals to Kroki post

See merge request hifis/hifis.net!238

Update 2021-06-10-story-hts.md, repositioned paragraph about tests from HelmholtzAI section to 'what has been done'

Update 2021-06-10-story-hts.md, added detailed numbers and enhanced the information in the HTS blog post.

Update Registration Link and Tutors for 2021-06-11-git-and-gitlab.md

See merge request hifis/hifis.net!240