add v3.0.0 changelog

Author: dcastil

docs/changelog/v3-changelog.md

@@ -0,0 +1,36 @@
+# Changelog for v3 releases
+
+## v3.0.0
+
+[Tailwind CSS v4 is here](https://tailwindcss.com/blog/tailwindcss-v4) and it's time to upgrade tailwind-merge to support it. tailwind-merge v3.0.0 is more accurate than ever and follows the Tailwind CSS spec more closely than in v2. That is thanks to Tailwind CSS v4 being more consistent than ever.
+
+Check out the [migration guide](./v2-to-v3-migration.md) and if you have any questions, feel free to [create an issue](https://github.com/dcastil/tailwind-merge/issues/new/choose).
+
+### Breaking Changes
+
+- Dropping support for Tailwind CSS v3 in favor of support for Tailwind CSS v4 by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- Theme scales keys changed and now match Tailwind CSS v4 theme variable namespace exactly by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- `isLength` validator was removed and split into separate validators `isNumber` and `isFraction` by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- Prefix defined in config shouldn't include combining `-` character anymore by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- Tailwind CSS v3 prefix position in class not supported anymore in favor of Tailwind CSS v4 position by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- New mandatory `orderSensitiveModifiers` property in config when using `createTailwindMerge`, etc. by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- `DefaultThemeGroupIds` type union consists of different string literals than before by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- Classes removed in Tailwind CSS v4 are not supported by tailwind-merge anymore by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+
+### New Features
+
+- Support for new important modifier position at the end of class by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- Support for arbitrary CSS variable syntax by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+- There are a bunch of new validators used by tailwind-merge, primarily for new Tailwind CSS v4 features like arbitrary CSS variables by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+
+### Bug Fixes
+
+- Previously some order-sensitive modifiers like `before:` were treated as not order-sensitive. This is now fixed by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+
+### Documentation
+
+- Added section explaining order-sensitive modifiers to [configuration docs](../configuration.md#order-sensitive-modifiers) by [@dcastil](https://github.com/dcastil) in [#518](https://github.com/dcastil/tailwind-merge/pull/518)
+
+**Full Changelog**: [`v2.6.0...v4.0.0`](https://github.com/dcastil/tailwind-merge/compare/v2.6.0...v4.0.0)
+
+Thanks to [@brandonmcconnell](https://github.com/brandonmcconnell), [@manavm1990](https://github.com/manavm1990), [@langy](https://github.com/langy), [@jamesreaco](https://github.com/jamesreaco), [@roboflow](https://github.com/roboflow), [@syntaxfm](https://github.com/syntaxfm), [@getsentry](https://github.com/getsentry), [@codecov](https://github.com/codecov), a private sponsor for sponsoring tailwind-merge! ❤️