[BUG] Text is invisible for example blocks in dark mode

**Describe the bug**
When looking at an an example block in the sparse memory section in dark mode, the text is invisible.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to https://docs.vulkan.org/spec/latest/chapters/sparsemem.html#sparsememory-accessing-unbound
2. Switch to dark mode
3. Example block shows up as white text on white background - the only visible thing is a hyperlink for [VK_FORMAT_R8_UNORM](https://docs.vulkan.org/spec/latest/chapters/formats.html#VkFormat).

**Expected behavior**
The text should all be visible, with the example block background changing to match dark mode so the lighter text shows up.

**Screenshots**

**Desktop (please complete the following information):**
- OS: Windows 10 (64-bit)
- Browser: Firefox
- Version: 147.0.3 (64-bit)