message: fix core concepts url
diff: @@ -17,7 +17,7 @@ or
  ## Providing your own theme
  -You can provide your own theme to Primer Components! There are a few ways of doing this to varying degrees, checkout the [theme docs](https://primer.style/components/docs/primer-theme) for more information.
  +You can provide your own theme to Primer Components! There are a few ways of doing this to varying degrees, checkout the [theme docs](https://primer.style/components/primer-theme) for more information.
  ## The `css` prop
  When push comes to shove and you just _really_ need to add a custom CSS rule, you can do that with the `css` prop. Please don't abuse this :)
  