[toc] markdown extension doesn't support multiple headers with identical content

[benintech]

Operating system

Android

Joplin version

2.13.10

Desktop version info

2.13.8

Current behaviour

Same behavior on both Linux (2.5.8) and Android (2.5.10). I guess on other platforms too.

When there are multiple headers with the same content (for example, ## mySubtitle and ## mySubtitle), clicking on the second instance in the table of content ([toc]) doesn't redirect to that second instance (nothing happens). It seems the [toc] markdown extension doesn't support multiple headers with identical content, only the first instance of the header works when clicking on it in the TOC.

Expected behaviour

Each TOC entry should redirect to the corresponding header.
Having multiple headers or sub-headers with the same content is something that can happen (e.g., having multiple identical subtitles, like # Title1 → ## mySubtitle and # Title2 → ## mySubtitle. I think Joplin's [toc] implementation should support that.

Logs

No response

[personalizedrefrigerator]

For context, this is the generated HTML:

<nav class="table-of-contents">
    <ul>
        <li><a href="#toc-test">Toc test</a></li>
        <li><a href="#test">test</a></li>
        <li><a href="#test-1">test</a></li>
    </ul>
</nav>
<h1 id="toc-test" class="maps-to-line" source-line="2" source-line-end="3">Toc test</h1>
<h1 id="test" class="maps-to-line" source-line="4" source-line-end="5">test</h1>
<p class="maps-to-line" source-line="6" source-line-end="7">This is a test.</p>
<h1 id="test-2" class="maps-to-line" source-line="8" source-line-end="9">test</h1>
<p class="maps-to-line" source-line="10" source-line-end="11">Testing...</p>

Observe that the second test link in the table of contents links to a non-existent heading with id test-1 (headings have IDs toc-test, test, and test-2).