chore(cli): split compilers

packages/vant-cli/src/compiler/compile-less.ts

@@ -0,0 +1,11 @@
+import { readFileSync } from 'fs-extra';
+import { render as renderLess } from 'less';
+
+export async function compileLess(filePath: string) {
+  const source = readFileSync(filePath, 'utf-8');
+  const { css } = await renderLess(source, {
+    filename: filePath
+  });
+
+  return css;
+}