docs(changelog): add v0.27.1 release notes

[zwpaper]

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[Copilot]

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CHANGELOG.md:12

• The release notes for v0.27.1 reference the full release note of v0.27.0. Please confirm if this is intentional or update the link to refer to the correct version.

* This is a patch release, please also check [the full release note](https://github.com/TabbyML/tabby/releases/tag/v0.27.0) for 0.27.

.changes/v0.27.1.md:5

• The release notes for v0.27.1 reference the full release note of v0.27.0. Please confirm if this is intentional or update the link to refer to the correct version.

* This is a patch release, please also check [the full release note](https://github.com/TabbyML/tabby/releases/tag/v0.27.0) for 0.27.