Add prettier
- Add prettier dependency
- Add
.prettierignore
based on existing.gitignore
- Add
.prettierrc
based on https://gitlab.com/gitlab-org/gitlab-vscode-extension/-/blob/f5b619566e7d4b01a0bdd19ccc1a7cc14806fb35/.prettierrc - Add yarn script
lint
- Add CI job for
yarn lint