test: add lint rule for single h1

We should never have more than one h1 on a page.

Signed-off-by: David Karlsson <[email protected]>

Author: dvdksn

.markdownlint.json

@@ -2,6 +2,7 @@
   "default": false,
   "hr-style": true,
   "heading-start-left": true,
+  "single-h1": true,
   "no-missing-space-atx": true,
   "no-multiple-space-atx": true,
   "no-missing-space-closed-atx": true,

content/config/formatting.md

@@ -97,7 +97,7 @@ $ docker inspect --format "{{upper .Name}}" container
 $ docker inspect --format='{{range .NetworkSettings.Networks}}{{println .IPAddress}}{{end}}' container
 ```
 
-# Hint
+## Hint
 
 To find out what data can be printed, show all content as json:
 

content/engine/reference/commandline/README.md

@@ -22,12 +22,12 @@ The output files are composed from two sources:
   Specifically, the Markdown inside the `## Description` and `## Examples`
   headings are parsed. Submit corrections to the text in those repositories.
 
-# Updating the YAML files
+## Updating the YAML files
 
 The process for generating the YAML files is still in flux. Check with
 @thaJeztah. Be sure to generate the YAML files with the correct
 release branch of `docker/cli`, for example, the `19.03` branch.
 
 After generating the YAML files, replace the YAML files in
 [https://github.com/docker/docs/tree/main/_data/engine-cli](https://github.com/docker/docs/tree/main/_data/engine-cli)
-with the newly-generated files. Submit a pull request.
+with the newly-generated files. Submit a pull request.

content/engine/tutorials/_index.md

@@ -7,9 +7,9 @@ aliases:
 - /engine/userguide/containers/
 ---
 
-# Learn by example
+Learn by example:
 
 * [Network containers](networkingcontainers.md)
 * [Manage data in containers](../../storage/volumes.md)
 * [Samples](../../samples/index.md)
-* [Get Started](../../get-started/index.md)
+* [Get Started](../../get-started/index.md)