Improve repository.

- add kokuwa checkstyle
- add dependabot
- add dependency documentation
- add code owners
- add codeql
- add license badge

.github/workflows/lint.yaml

@@ -0,0 +1,26 @@
+name: Lint
+
+"on":
+  workflow_dispatch: {}
+  push:
+    branches: [main]
+  pull_request: {}
+
+jobs:
+
+  yaml:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.4.0
+      - uses: ibiqlik/action-yamllint@v3.1.0
+        with:
+          format: colored
+          strict: true
+
+  markdown:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.4.0
+      - uses: avto-dev/markdown-lint@v1.5.0
+        with:
+          args: /github/workspace