Add packages to optimize svgs dynamically

These packages will be used to dynamically optimize SVG images
during the build.

R=jacktfranklin@chromium.org

Bug: 1216402
Change-Id: I04e95aa7d79c9d67beaf8a7861182c52b16b7d0f
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2939992
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>
Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
diff --git a/node_modules/css-tree/lib/walker/index.js b/node_modules/css-tree/lib/walker/index.js
new file mode 100644
index 0000000..f3f0d6d
--- /dev/null
+++ b/node_modules/css-tree/lib/walker/index.js
@@ -0,0 +1,4 @@
+var createWalker = require('./create');
+var config = require('../syntax/config/walker');
+
+module.exports = createWalker(config);