Bump app version and required core version to 3.0

pyproject.toml

 [tool.poetry]
 name = "AlekSIS-App-Resint"
-version = "2.2.1.dev0"
+version = "3.0dev0"
 packages = [
     { include = "aleksis" }
 ]
@@ -41,7 +41,7 @@ secondary = true
 
 [tool.poetry.dependencies]
 python = "^3.9"
-AlekSIS-Core = "^2.1"
+AlekSIS-Core = "^3.0dev3"
 
 [tool.poetry.dev-dependencies]
 aleksis-builddeps = "*"