add redirect for URL hard-coded into the default proguard config file,
and update related redirects for the entire /guide/developing/ path.

Change-Id: Ie23791e3765ff821d9abba220ebdde782d6439ed
diff --git a/docs/html/_redirects.yaml b/docs/html/_redirects.yaml
index cf56f2b..11e06f1 100644
--- a/docs/html/_redirects.yaml
+++ b/docs/html/_redirects.yaml
@@ -149,9 +149,11 @@
   to: /google/play/licensing/index.html
 - from: /google/play/billing/billing_about.html
   to: /google/play/billing/index.html
-- from: /guide/developing/tools/
+- from: /guide/developing/tools/proguard.html
+  to: /studio/build/shrink-code.html
+- from: /guide/developing/tools/...
   to: /studio/command-line/
-- from: /guide/developing/
+- from: /guide/developing/...
   to: /studio/
 - from: /tools/aidl.html
   to: /guide/components/aidl.html