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/bson.md

@@ -61,6 +61,41 @@ The library uses the following mapping from JSON values types to BSON types:
     ```
 
 
+
+
+
+
+### Byte layout
+
+Consider the following JSON value (shown formatted for readability):
+
+```json
+{
+  "id": 300,
+  "name": "json",
+  "pi": 3.14,
+  "tags": [
+    "a",
+    "b"
+  ]
+}
+```
+
+`to_bson` encodes it to 69 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-l">45 00 00 00</span></td><td>document size: 69 bytes (int32, little-endian)</td></tr>
+<tr><td><code>&quot;id&quot;: 300,</code></td><td><span class="bl bl-t">10</span> <span class="bl bl-d">69 64 00</span> <span class="bl bl-d">2C 01 00 00</span></td><td>int32 element; key as NUL-terminated string; value (little-endian)</td></tr>
+<tr><td><code>&quot;name&quot;: &quot;json&quot;,</code></td><td><span class="bl bl-t">02</span> <span class="bl bl-d">6E 61 6D 65 00</span> <span class="bl bl-l">05 00 00 00</span> <span class="bl bl-d">6A 73 6F 6E 00</span></td><td>string element; key; length incl. NUL (int32); NUL-terminated UTF-8 bytes</td></tr>
+<tr><td><code>&quot;pi&quot;: 3.14,</code></td><td><span class="bl bl-t">01</span> <span class="bl bl-d">70 69 00</span> <span class="bl bl-d">1F 85 EB 51 B8 1E 09 40</span></td><td>double element; key; value (little-endian)</td></tr>
+<tr><td><code>&quot;tags&quot;: [</code></td><td><span class="bl bl-t">04</span> <span class="bl bl-d">74 61 67 73 00</span> <span class="bl bl-l">17 00 00 00</span></td><td>array element; key; embedded document of 23 bytes (keys are the indices)</td></tr>
+<tr><td><code>&quot;a&quot;,</code></td><td><span class="bl bl-t">02</span> <span class="bl bl-d">30 00</span> <span class="bl bl-l">02 00 00 00</span> <span class="bl bl-d">61 00</span></td><td>string element; key <code>&quot;0&quot;</code>; length 2; <code>a</code> + NUL</td></tr>
+<tr><td><code>&quot;b&quot;</code></td><td><span class="bl bl-t">02</span> <span class="bl bl-d">31 00</span> <span class="bl bl-l">02 00 00 00</span> <span class="bl bl-d">62 00</span></td><td>string element; key <code>&quot;1&quot;</code>; length 2; <code>b</code> + NUL</td></tr>
+<tr><td><code>]</code></td><td><span class="bl bl-t">00</span></td><td>end of the array document</td></tr>
+<tr><td><code>}</code></td><td><span class="bl bl-t">00</span></td><td>end of the document</td></tr>
+</tbody></table></div>
+
 ## Deserialization
 
 The library maps BSON record types to JSON value types as follows: