chore: Add lcov coverage output to vitest (#7987)

chore: Add lcov coverage output to vitest so VSCode coverage gutters extension works

Signed-off-by: Mark Tolmacs <mark@lazycat.hu>

vitest.config.mts

@@ -6,7 +6,7 @@ export default defineConfig({
     globals: true,
     environment: "jsdom",
     coverage: {
-      reporter: ["text", "json-summary", "json", "html"],
+      reporter: ["text", "json-summary", "json", "html", "lcovonly"],
       thresholds: {
         lines: 70,
         branches: 70,