add .pre-commit-config.yaml,.yamllint

* also add readme badge for pre-commit

.pre-commit-config.yaml

@@ -0,0 +1,40 @@
+---
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.0.1
+    hooks:
+      - id: check-merge-conflict
+      - id: check-toml
+      - id: check-yaml
+        exclude: .drone.yml  # drone's yaml is somewhat strange sometimes
+  - repo: local
+    hooks:
+      - id: hugo-version-check
+        name: hugo version check
+        entry: |
+          bash -c "
+            files='.drone.yml Dockerfile'
+            count=$(grep -oE '( |hugo-v)[0-9].[0-9].[0-9].[0-9]' $files | cut -d':' -f2 | sed -e 's/^ *//g' -e 's/hugo-v//g' | uniq | wc -l)
+            if [ $count -gt 1 ]; then
+              echo hugo versions inconsistent:
+              grep -noE --color=always '( |hugo-v)[0-9].[0-9].[0-9].[0-9]' $files
+              exit 1
+            fi
+          "
+        language: system
+        pass_filenames: false
+      - id: check-compose-file
+        name: check compose file
+        language: system
+        entry: docker-compose -f docker-compose.yml config
+        pass_filenames: false
+      - id: yamllint
+        name: yamllint
+        language: system
+        entry: yamllint .
+        pass_filenames: false
+  - repo: https://git.dotya.ml/wanderer/hadolint-pre-commit
+    rev: v0.0.1
+    hooks:
+      - id: hadolint-container
+...

.yamllint

@@ -0,0 +1,13 @@
+---
+
+yaml-files:
+  - '*.yaml'
+  - '*.yml'
+  - '.yamllint'
+
+rules:
+  line-length:
+    level: warning
+
+# vim: ft=yaml bs=2 ts=2
+...

README.md

@@ -1,5 +1,6 @@
 # [`docs`](https://git.dotya.ml/dotya.ml/docs/src/branch/master)
 
+[![pre-commit](https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white)](https://github.com/pre-commit/pre-commit)
 [![Build Status](https://drone.dotya.ml/api/badges/dotya.ml/docs/status.svg)](https://drone.dotya.ml/dotya.ml/docs)
 
 sawce of the dotya.ml's docs site.