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/features/binary_formats/messagepack.md

@@ -91,6 +91,41 @@ specification:
     --8<-- "examples/to_msgpack.output"
     ```
 
+
+
+
+
+### Byte layout
+
+Consider the following JSON value (shown formatted for readability):
+
+```json
+{
+  "id": 300,
+  "name": "json",
+  "pi": 3.14,
+  "tags": [
+    "a",
+    "b"
+  ]
+}
+```
+
+`to_msgpack` encodes it to 39 bytes (shown in hexadecimal; the encoding contains no whitespace). The colors mark the role of each byte: <span class="bl bl-t">type/marker</span> <span class="bl bl-l">length/count/size</span> <span class="bl bl-d">data</span>.
+
+<div class="byte-layout" markdown="0"><table>
+<thead><tr><th>JSON</th><th>Bytes</th><th>Meaning</th></tr></thead><tbody>
+<tr><td><code>{</code></td><td><span class="bl bl-t">84</span></td><td>map with 4 key/value pairs</td></tr>
+<tr><td><code>&quot;id&quot;: 300,</code></td><td><span class="bl bl-t">A2</span> <span class="bl bl-d">69 64</span> <span class="bl bl-t">CD</span> <span class="bl bl-d">01 2C</span></td><td>key: fixstr of length 2, then its UTF-8 bytes; value: uint 16 (big-endian)</td></tr>
+<tr><td><code>&quot;name&quot;: &quot;json&quot;,</code></td><td><span class="bl bl-t">A4</span> <span class="bl bl-d">6E 61 6D 65</span> <span class="bl bl-t">A4</span> <span class="bl bl-d">6A 73 6F 6E</span></td><td>key: fixstr of length 4; value: fixstr of length 4</td></tr>
+<tr><td><code>&quot;pi&quot;: 3.14,</code></td><td><span class="bl bl-t">A2</span> <span class="bl bl-d">70 69</span> <span class="bl bl-t">CB</span> <span class="bl bl-d">40 09 1E B8 51 EB 85 1F</span></td><td>key: fixstr of length 2; value: float 64 (IEEE 754, big-endian)</td></tr>
+<tr><td><code>&quot;tags&quot;: [</code></td><td><span class="bl bl-t">A4</span> <span class="bl bl-d">74 61 67 73</span> <span class="bl bl-t">92</span></td><td>key: fixstr of length 4; value: fixarray with 2 elements</td></tr>
+<tr><td><code>&quot;a&quot;,</code></td><td><span class="bl bl-t">A1</span> <span class="bl bl-d">61</span></td><td>fixstr of length 1</td></tr>
+<tr><td><code>&quot;b&quot;</code></td><td><span class="bl bl-t">A1</span> <span class="bl bl-d">62</span></td><td>fixstr of length 1</td></tr>
+<tr><td><code>]</code></td><td></td><td>no end marker: the element count was given up front</td></tr>
+<tr><td><code>}</code></td><td></td><td>no end marker: the member count was given up front</td></tr>
+</tbody></table></div>
+
 ## Deserialization
 
 The library maps MessagePack types to JSON value types as follows: