Add GitLab CI/CD template support

[naokihaba]

We've received several requests for a GitLab CI/CD version of our existing Vite+ GitHub Action. Currently, we only provide voidzero-dev/setup-vp for GitHub, leaving GitLab users without an official, reusable setup method. You can find more details in this issue: voidzero-dev/vite-plus#1920

Objective

Our goal is to add official GitLab CI/CD support, enabling users to easily integrate a Vite+ setup template directly into their .gitlab-ci.yml.

For example, users should be able to use the following:

include:
  - remote: 'https://raw.githubusercontent.com/voidzero-dev/setup-vp/v1/gitlab/setup-vp.yml'

The template should replicate the functionality of the GitHub Action, including Node.js and package manager setup, Vite+ installation, and dependency caching.

Proposed Changes

I propose adding a dedicated folder for the GitLab CI template:

gitlab/
└── setup-vp.yml

Since GitLab supports remote YAML includes, hosting the template in this repository will work seamlessly as long as it remains public.

For more information on how this works, please refer to the GitLab documentation:

• https://docs.gitlab.com/ci/yaml/#includeremote
• https://docs.gitlab.com/ci/migration/github_actions/

I will take care of this implementation.