[#1808] .github: Add changelog workflow

It checks whether the CHANGELOG.md was updated in a just-created PR.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

.github/workflows/changelog.yml

@@ -0,0 +1,28 @@
+name: CHANGELOG check
+
+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    name: Check for updates
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Get changed CHANGELOG
+        id: changelog-diff
+        uses: tj-actions/changed-files@v29
+        with:
+          files: CHANGELOG.md
+
+      - name: Fail if changelog not updated
+        if: steps.changelog-diff.outputs.any_changed == 'false'
+        uses: actions/github-script@v3
+        with:
+          script: |
+            core.setFailed('CHANGELOG.md has not been updated')

CHANGELOG.md

@@ -5,6 +5,8 @@ Changelog for NeoFS Node
 
 ### Added
 
+- Changelog updates CI step (#1808)
+
 ### Changed 
 
 ### Fixed