feature request(headerid): Markdown support

@ionelmc, @albertodonato, @stevepiercy

1. Summary

It would be nice if Markdown users can use headerid.

2. MCVE

2.1. The part of pelicanconf.py

PLUGINS = [
    'headerid'
]

2.2. KiraArticle.md

Title: KiraArticle
Date: 2020-09-24 18:57:33

<!-- MarkdownTOC -->

1. [**Кира Богиня!**](#Кира-Богиня)

<!-- /MarkdownTOC -->

<a id="Кира-Богиня"></a>
# Кира Богиня!

Kira Goddess!

2.3. Command

pelican content -s pelicanconf.py --ignore-cache

2.4. Behavior

2.4.1. Current

headerid doesn’t add permalink.

<p><a id="Кира-Богиня"></a></p>
<h1>Кира Богиня!</h1>

2.4.2. Desired

Adding permalink.

<p><a id="Кира-Богиня"></a></p>
<h1>Кира Богиня! <a class="headerlink" href="#Кира-Богиня" title="Permalink to this headline">*</a></h1>

3. Markdown TOC plugin

From headerid documentation:

For Markdown, this plugin is less relevant since the Python-Markdown library includes a Table of Contents extension that will generate link anchors. To enable the toc extension, add a line similar to the following example to your Pelican settings file

But I use MarkdownTOC Sublime Text package instead of “Table of Contents” Python Markdown extension. I can use “Table of Contents” Python Markdown extension, adding to my pelicanconf.py these lines:

MARKDOWN = {
    'extension_configs': {
        'markdown.extensions.toc': {
            'permalink': 'true'
        },
    },
    'output_format': 'html5',
}

But I get in the output:

<h1 id="_1">Кира Богиня!<a class="headerlink" href="#_1" title="Permanent link">&para;</a></h1>

“Table of Contents” doesn’t support non-ASCII symbols in headers. It adds href="#_1" instead of href="#Кира-Богиня". Also in “Table of Contents”, unlike MarkdownTOC, users haven’t ability to determine which characters to remove from id. “Table of Contents” doesn’t have other MarkdownTOC options.

I don’t think that “Table of Contents” is a better solution, and I think it would be nice if the headerid plugin could be used by Markdown users who don’t use “Table of Contents”.

Thanks.

getpelican / pelican-plugins