[Enhancement]: Add Dark color scheme toggle for Mkdocs

[kylelmh]

Proposal

I believe testcontainer's mkdocs has its own color scheme, but a dark mode would be greatly appreciated. Would a pull request for adding the default dark colors be welcomed? i.e.

mkdocs.yml

theme:
  palette: 
    - scheme: testcontainers
+     toggle:
+       icon: material/brightness-7 
+       name: Switch to dark mode
+
+   - scheme: slate
+     toggle:
+       icon: material/brightness-4
+       name: Switch to light mode