Bump version to 0.21.0; rework changelog, contributors, and docs

Release:
- Bump version to 0.21.0 and regenerate tusb_option.h, library.json,
  repository.yml, sonar-project.properties, boards.rst, dependencies.rst
- Add 0.21.0 release notes and split the changelog into per-release files
  under docs/info/changelog/ (date out of title, driver/class groups as
  sub-headings, DCD & HCD section after Device/Host stacks)

Contributors:
- Credit each release's PR authors in a Contributors section
- Drop the curated contributors page; add MAINTAINERS.rst

Docs:
- Update Code of Conduct to Contributor Covenant 3.0 (keep it in the repo,
  remove it from the built docs)
- Sidebar: add a home entry, rename the group to "Documentation", move
  Changelog into it, add a GitHub Sponsor button, merge external links,
  rename FAQ; hide the inline toctree on the landing page
- Add the make-release skill and update the AGENTS.md release process

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/library.json b/library.json
index efad438a7..7e2febb0c 100644
--- a/library.json
+++ b/library.json
@@ -1,6 +1,6 @@
 {
     "name": "TinyUSB",
-    "version": "0.20.0",
+    "version": "0.21.0",
     "description": "TinyUSB is an open-source cross-platform USB Host/Device stack for embedded system, designed to be memory-safe with no dynamic allocation and thread-safe with all interrupt events are deferred then handled in the non-ISR task function.",
     "keywords": "usb, host, device",
     "repository":