Remove leading slashes, sort .dockerignore

.dockerignore

-/ansible
-/venv
-/clusters
-/docs
-/.git
-/.direnv
-/.envrc
-/CHANGELOG.md
-/.direnv
-/Dockerfile
-/.dockerignore
-/flux2
-/.gitignore
-/.gitlab
-/.gitlab-ci.yml
-/.gitlint
-/install
-/Makefile
-/.pre-commit-config.yaml
+.direnv
+.direnv
+.dockerignore
+.envrc
+.git
+.gitignore
+.gitlab
+.gitlab-ci.yml
+.gitlint
+.pre-commit-config.yaml
+.renovaterc.json
+.sourceignore
+CHANGELOG.md
+Dockerfile
+Makefile
 README.md
-/.renovaterc.json
-/.sourceignore
-/stackspin
-/upgrade-scripts
 VERSION
+ansible
+clusters
+docs
+flux2
+install
+stackspin
+upgrade-scripts
+venv