Patch 238 darkmode

[ThePhisch]

Also added a VS Code Devcontainer and updated dependencies

The pipeline for the creation of the rucio-docs for the client API is as
follows:

• begin process using build_documentation.sh
• generate_dynamic_files.sh spins up a docker container
• inside of the docker container, generate_docs.sh is called
• which in turn calls generate_client_api_docs.sh
• generate_client_api_docs.sh parses the files in lib/rucio/client
  and converts them using pydoc-markdown.
• pydoc-markdown uses rucio_processor.py and rucio_renderer.py
  (both in tools/run_in_docker, which is mounted into the docker
  container).
• "auto_generated" output markdown files' ownerships are changed
• compiling this markdown into html -> completed using docusaurus as
  part of the github action

The final stage adds styling (i.e. CSS) to the compiled markdown files.
This means that in general, a dark mode can be applied. However, some
components in the client api are formatted in pre-styled HTML tables
(within the markdown!), these styles are never overridden.

As discussed with @bari12, a simple fix to the missing dark mode is
proposed here. Instead of reworking the markdown to use plain
markdown-tables which are styled at the appropriate (docusaurus) step
(and not HTML tables that come with their own style), we reference a
docusaurus CSS variable --ifm-background-color, which will set the
correct dark mode colour (depending on whether dark or light mode is
requested).

We are aware of the fact that in doing so, we reference a variable
several steps before it is defined. In addition, we add even more
complicated HTML/CSS syntax to markdown, which is supposed to be easy on
human eyes. The benefit of this fix is that it is minimally-invasive,
and that the markdown files are never supposed to be served by
themselves and only act as a middle step for the entire pipeline.

[maany]

Could you also update README.md with the pipeline you mentioned in the issue description? It could be helpful for the next person who jumps in to debug stuff here :)

[ThePhisch]

Could you also update README.md with the pipeline you mentioned in the issue description? It could be helpful for the next person who jumps in to debug stuff here :)

done

[maany]

Looks good :)