Configure CircleCI to run markdownlint

.circleci/config.yml

@@ -0,0 +1,22 @@
+version: 2
+
+workflows:
+  version: 2
+  any-commit:
+    jobs:
+      - lint
+
+jobs:
+  lint:
+    docker: # run the steps with Docker
+      - image: circleci/node:12.6 # ...with this image as the primary container; this is where all `steps` will run
+    steps:
+      - checkout
+      - run:
+          name: install-markdownlint
+          command: |
+            sudo npm install -g markdownlint-cli
+            markdownlint --version
+      - run:
+          name: lint
+          command: markdownlint .

.markdownlint.json

@@ -0,0 +1,9 @@
+{
+  "default": true,
+
+  "line_length": false,
+  "no-bare-urls": false,
+
+  "comment": "Ignore errors like MD026/no-trailing-punctuation Trailing punctuation in heading [Punctuation: '?'] in README.md's title",
+  "no-trailing-punctuation": false
+}