Convert Markdown to HTML with GitLab

[k-deeley]

Nice alternative, also allows private conversion.

https://docs.gitlab.com/ee/api/markdown.html#render-an-arbitrary-markdown-document

This works:

request = matlab.net.http.RequestMessage( method, [], struct( "text", md, "gfm", true ) );
request = addFields( request, "Content-Type", "application/json" );
request = addFields( request, "PRIVATE-TOKEN", getSecret("GitLab API token") );
uri = matlab.net.URI( "https://insidelabs-git.mathworks.com/api/v4/markdown" );
response = request.send( uri );

It's not possible to create a "just authenticate" token in GitLab. I don't know what is the lowest set of permissions that will work.

Looks like "API" which is everything the user can do.

Differences between GitLab and GitHub returned HTML:

• GitLab MATLAB blocks are in: <pre data-sourcepos="34:1-36:3" data-canonical-lang="matlab" class="code highlight js-syntax-highlight language-matlab" lang="matlab" v-pre="true"> in <div class="gl-relative markdown-code-block js-markdown-code">
• Some emojis don't convert, e.g., 🦛 😞

Otherwise the styling is clean. When the GitHub CSS is applied, everything except syntax highlighting looks the same.

[djmsampson]

In terms of supporting the different styling this can be achieved in two ways:

1. manipulating the HTML in docconvert
2. augmenting the stylesheet

The latter requires no MATLAB code changes, but we then need to merge subsequent changes to github-markdown.css. (In practice this has been less frequent than annually.)

[djmsampson]

The generated HTML for MATLAB input and output from GitHub is of form:

<div class="highlight highlight-source-matlab"><pre>...</pre></div>
<div class="highlight highlight-output-matlab"><pre>...</pre></div>

[djmsampson]

Fixed in #17