docs: Update ChangeLog for 12.3.0
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+2026-05-18 Mintsuki <mintsuki@protonmail.com>
+
+ *** Release 12.3.0 ***
+
+ Noteworthy changes compared to the previous release, 12.2.0:
+
+ New features:
+ - Add support for fractional timeout values.
+
+ Miscellaneous:
+ - Significantly improve framebuffer performance on some machines by
+ using the Write Combining caching mode via PAT and page tables on
+ x86-64/UEFI instead of MTRRs.
+ - Improve reliability of the MTRR framebuffer Write Combining path on
+ IA-32 (UEFI and BIOS).
+
2026-05-07 Mintsuki <mintsuki@protonmail.com>
*** Release 12.2.0 ***
