[bug] Code spans aren't HTML escaped in markdown posts

[autumnull]

Describe the bug with a clear and concise description of what the bug is.

When using the markdown format, code spans (like this) containing HTML aren't HTML-escaped during processing.

What's your GoToSocial Version?

v0.3.6

GoToSocial Arch

armv7 Binary

What happened?

making a post with the markdown format with the following contents

`Nobody tells you about the </code><del>SECRET CODE</del><code>, do they?`

results in a post with this content:

<p><code>Nobody tells you about the </code><del>SECRET CODE</del><code>, do they?</code></p>

which is rendered as this:

Nobody tells you about the SECRET CODE, do they?

What you expected to happen?

should result in the following HTML (or similar):

<p><code>Nobody tells you about the &lt;/code&gt;&lt;del&gt;SECRET CODE&lt;/del&gt;&lt;code&gt;, do they?</code></p>

which is rendered as this:

Nobody tells you about the </code><del>SECRET CODE</del><code>, do they?

How to reproduce it?

Get an oauth token, send a request to make a new post in markdown format with the content above.

Anything else we need to know?

No response

[tsmethurst]

Thanks! I'll check it out soon :)