Improve documentation: byte layouts, release pages, See also, dark-mode images (#5906)

- Make the iterator range illustrations legible in dark mode (prefers-color-scheme
  rules inside the SVGs).
- Add a "Byte layout" section with a color-coded byte table to each binary format
  page (BJData, BON8, BSON, CBOR, MessagePack, UBJSON), and highlight the smallest
  size per file in the comparison table.
- Add "See also" sections to the overview pages that lacked one.
- Split the release notes into one page per release, grouped by minor version on
  the overview page, with an "API changes" section per release generated from the
  API pages' version histories (hooks/api_changes.py).
- Fact-check the release notes and version histories against the release tags and
  correct wrong or misleading entries (e.g., json_serializer 2.1.0, merge_patch
  3.1.0, items, count, operator[], to_bjdata, std::string_view key support).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/basic_json/items.md

@@ -104,8 +104,8 @@ When iterating over an array, `key()` will return the index of the element as st
 
 ## Version history
 
-- Added `iterator_wrapper` in version 3.0.0.
-- Added `items` and deprecated `iterator_wrapper` in version 3.1.0.
+- Added in version 3.1.0 as the replacement of the static function `iterator_wrapper`, which was available since
+  version 1.0.0 and is deprecated since version 3.1.0.
 - Added structured binding support in version 3.5.0.
 
 !!! warning "Deprecation"