docs: restore missing CHANGELOG entries for 1.20.14 and 1.20.16-1.20.23

[laurentiu021]

The CHANGELOG skipped eleven published releases — it jumped from ## [1.20.24] straight to ## [1.20.15], and 1.20.14's entry was stacked under the 1.20.15 header instead of having its own. All eleven versions (1.20.14, 1.20.16–1.20.23) have git tags and published GitHub releases.

Fix (CHANGELOG.md, docs-only, no release)

• Inserted the missing ## [1.20.16] through ## [1.20.23] sections between 1.20.24 and 1.20.15.
• Split the stacked 1.20.14 content out into its own ## [1.20.14] header between 1.20.15 and 1.20.13.
• Content reconstructed verbatim from each version's published GitHub release body (per-version delta computed by diffing each release body against its predecessor, since the release notes stack history). No invented entries.

The CHANGELOG is now contiguous 1.20.24 → 1.20.13 with one header per released tag.

docs: — no code change, no release.