docs: release notes for the v21.2.12 release

Author: alxhub

CHANGELOG.md

@@ -1,3 +1,21 @@
+<a name="21.2.12"></a>
+# 21.2.12 (2026-05-06)
+### core
+| Commit | Type | Description |
+| -- | -- | -- |
+| [fe13bb669d](https://github.com/angular/angular/commit/fe13bb669d2bfab4713623d17b41c430aa0a61d8) | fix | allow explicit read generic with signal input transforms |
+| [3430251fef](https://github.com/angular/angular/commit/3430251fef93f6aec1fa9c7867e85df23f67c9a0) | fix | i18n flags leaking on errors |
+| [1aeebbe304](https://github.com/angular/angular/commit/1aeebbe3048b5aa612dd0a5448de9883ed51e7e8) | fix | respect ngSkipHydration on components with projectable nodes in LContainers |
+| [9e38ed7d57](https://github.com/angular/angular/commit/9e38ed7d5773a9193ba07afdba3f7a9f2fe02d18) | fix | sanitizer typings |
+| [7a05a9a71a](https://github.com/angular/angular/commit/7a05a9a71a5ab75042ec5560c01526de6e61e062) | fix | validate security-sensitive attributes in i18n bindings |
+| [c37f6ca42f](https://github.com/angular/angular/commit/c37f6ca42f263353cb9563fa90d7b31d3c7837ca) | fix | visit ng-let expression value in signal migration schematics |
+### forms
+| Commit | Type | Description |
+| -- | -- | -- |
+| [03ad53863b](https://github.com/angular/angular/commit/03ad53863bf3c368f0f02a4322d4141e8f70f674) | fix | prohibit concurrent submits in signal forms |
+
+<!-- CHANGELOG SPLIT MARKER -->
+
 <a name="20.3.20"></a>
 # 20.3.20 (2026-05-06)
 ### core