CI: skip release.yml on doc-only changes

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Author: AkihiroSuda

.github/workflows/release.yml

@@ -3,14 +3,23 @@
 
 name: Release
 on:
+  # paths-ignore should be kept in sync with test.yml
   push:
     branches:
     - 'master'
     tags:
     - 'v*'
+    paths-ignore:
+    - "docs/**"
+    - "website/**"
+    - "**.md"
   pull_request:
     branches:
     - 'master'
+    paths-ignore:
+    - "docs/**"
+    - "website/**"
+    - "**.md"
 env:
   GO111MODULE: on
   GOTOOLCHAIN: local