fix: support requiring files with less extension (#3465)

Author: rluvaton

Diff for: packages/vitest/src/runtime/setup.node.ts

@@ -39,6 +39,7 @@ export async function setupGlobalEnv(config: ResolvedConfig) {
   _require.extensions['.css'] = () => ({})
   _require.extensions['.scss'] = () => ({})
   _require.extensions['.sass'] = () => ({})
+  _require.extensions['.less'] = () => ({})
 
   installSourcemapsSupport({
     getSourceMap: source => state.moduleCache.getSourceMap(source),

Diff for: test/core/src/file-less.less

@@ -0,0 +1,5 @@
+@color: red;
+
+.red {
+  color: @color;
+}

Diff for: test/core/test/require.test.ts

@@ -7,9 +7,11 @@ describe('using "require" to import a module', () => {
     const css = _require('./../src/file-css.css')
     const sass = _require('./../src/file-sass.sass')
     const scss = _require('./../src/file-scss.scss')
+    const less = _require('./../src/file-less.less')
 
     expect(css).toEqual({})
     expect(sass).toEqual({})
     expect(scss).toEqual({})
+    expect(less).toEqual({})
   })
 })