minor stuff that needs improvement

[jothepro]

Every time I visit the page I spot some small error.
This issue is a collection of these minor bugs that need to be fixed in the next update:

• Footer does not reach bottom. The lighter gray bar at the bottom should be removed.
  
• Link to intellij plugin docs in setup.md is broken
• Search index should not include landing page. When one searches "IDL", the first result is the marketing blabla from the landing page
• <kbd> tags are not readable in dark mode: