[TASK] Prepare release of version 9.0.0 (#1328)

Closes #1326

Author: oliverklee

.github/dependabot.yml

@@ -8,7 +8,7 @@ updates:
           interval: "daily"
       commit-message:
           prefix: "[Dependabot] "
-      milestone: 1
+      milestone: 9
 
     - package-ecosystem: "composer"
       directory: "/"
@@ -24,4 +24,4 @@ updates:
       versioning-strategy: "increase"
       commit-message:
           prefix: "[Dependabot] "
-      milestone: 1
+      milestone: 9

CHANGELOG.md

@@ -10,6 +10,20 @@ Please also have a look at our
 
 ### Added
 
+### Changed
+
+### Deprecated
+
+### Removed
+
+### Fixed
+
+### Documentation
+
+## 9.0.0: New features, deprecation removals and bug fixes
+
+### Added
+
 - Interface `RuleContainer` for `RuleSet` `Rule` manipulation methods (#1256)
 - Partial support for CSS Color Module Level 4:
     - `rgb` and `rgba`, and `hsl` and `hsla` are now aliases (#797}
@@ -43,8 +57,6 @@ Please also have a look at our
   #1187, #1190, #1192, #1193, #1203)
 - Add visibility to all class/interface constants (#469)
 
-### Deprecated
-
 ### Removed
 
 - Remove `getLineNo()` from these classes (use `getLineNumber()` instead):

composer.json

@@ -61,7 +61,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-main": "9.0.x-dev"
+            "dev-main": "9.1.x-dev"
         }
     },
     "scripts": {