fix(css_variables): update root directory

[colbat]

Problem

Root directory is incorrect for projects containing a package.json file in subdirectories.

For a project with a given file structure:

my-monorepo/
├── package.json
├── yarn.lock
├── css/
│   └── css-variables/
│       ├── color.css
│       └── typography.css
└── components/
    └── core/
        └── my-feature/
            ├── package.json           ← 2. causes LSP root to stop here
            ├── feature-component-a/
            │   └── feature-component-a.module.css           ← 1. current open buffer 
            └── feature-component-b/
                └── feature-component-b.module.css

The LSP is using my-feature as the root directory. This directory is not the one where the css variables are defined. It leads to an issue where the css variables are not indexed, and from feature-component-a.module.css auto-completion and jump to definition are not working.

Solution

Using the same root_dir logic as ts_ls (which prefers lockfiles like yarn.lock or .git as root markers) correctly sets the project root to my-monorepo/, allowing css/css-variables/ to be discoverable for the LSP.