A0-2005: Create yamllint configuration for linting YAML files in .github directory

.github/workflows/yaml-lint.yml

@@ -0,0 +1,39 @@
+---
+name: GH Action YAML linter
+
+on:
+  pull_request:
+    paths:
+      - ".github/**/**.yml"
+      - ".github/**/**.yaml"
+
+concurrency:
+  group: ${{ github.ref }}-${{ github.workflow }}
+  cancel-in-progress: true
+
+jobs:
+  main:
+    name: YAML Lint
+    runs-on: ubuntu-20.04
+    steps:
+      - name: GIT | Checkout source code
+        uses: actions/checkout@v3
+        with:
+          repository: Cardinal-Cryptography/aleph-node
+          token: ${{ secrets.CI_GH_TOKEN }}
+
+      - name: GIT | Check diff
+        id: check-diff
+        run: |
+          git fetch --quiet origin ${GITHUB_BASE_REF}:refs/remotes/origin/${GITHUB_BASE_REF}
+          YAML_FILES=`git --no-pager diff origin/${GITHUB_BASE_REF} --name-only \
+          | grep -E ".github\/.*\/.*(.yaml|.yml)" | tr '\n' ' '`
+          echo "Changed YAML files: ${YAML_FILES}"
+          echo "YAML_FILES=`echo $YAML_FILES`" >> $GITHUB_ENV
+
+      - name: LINT | Execute yaml-lint
+        uses: ibiqlik/action-yamllint@v3.1.1
+        with:
+          strict: true
+          file_or_dir: ${{ env.YAML_FILES }}
+          config_file: .yamllint

.yamllint

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+---
+extends: default
+
+rules:
+  braces:
+    min-spaces-inside: 0
+    max-spaces-inside: 0
+    min-spaces-inside-empty: -1
+    max-spaces-inside-empty: -1
+  brackets:
+    min-spaces-inside: 0
+    max-spaces-inside: 0
+    min-spaces-inside-empty: -1
+    max-spaces-inside-empty: -1
+  colons:
+    max-spaces-before: 0
+    max-spaces-after: 1
+  commas:
+    max-spaces-before: 0
+    min-spaces-after: 1
+    max-spaces-after: 1
+  comments:
+    level: warning
+    require-starting-space: true
+    min-spaces-from-content: 2
+  comments-indentation: disable
+  document-end: disable
+  document-start: enable
+  empty-lines:
+    max: 2
+    max-start: 1
+    max-end: 1
+  empty-values:
+    forbid-in-block-mappings: false
+    forbid-in-flow-mappings: false
+  hyphens:
+    max-spaces-after: 1
+  indentation:
+    spaces: consistent
+    indent-sequences: true
+    check-multi-line-strings: false
+  key-duplicates: enable
+  key-ordering: disable
+  line-length:
+    max: 100
+    level: error
+    allow-non-breakable-words: true
+    allow-non-breakable-inline-mappings: false
+  new-line-at-end-of-file: enable
+  new-lines:
+    type: unix
+  trailing-spaces: enable
+  truthy:
+    allowed-values:
+      - "true"
+      - "false"
+    check-keys: false