misc: correct .npmignore for node >=18.20 (#15924)

.npmignore

@@ -3,20 +3,20 @@
 # folders
 .vscode/
 .github/
-assets/
-build/
-coverage/
-proto/
-docs/
+/assets/
+/build/
+/coverage/
+/proto/
+/docs/
 
-core/scripts/*
-viewer/
-treemap/
-clients/
-cli/results/
-lighthouse-logger/
+/core/scripts/*
+/viewer/
+/treemap/
+/clients/
+/cli/results/
+/lighthouse-logger/
 **/test/**
-report/test-assets/
+/report/test-assets/
 
 # keep a few scripts useful for CI
 !core/scripts/manual-chrome-launcher.js
@@ -25,12 +25,12 @@ report/test-assets/
 
 # Exclude the CLI smoketests but keep the smoketest runner that is used
 # by downstream projects (e.g. publisher ads).
-!cli/test/smokehouse/**
-cli/test/smokehouse/test-definitions/
+!/cli/test/smokehouse/**
+/cli/test/smokehouse/test-definitions/
 
 results/
-lantern-data/
-timings-data/
+/lantern-data/
+/timings-data/
 
 # ignore all folders named as such
 node_modules