tick offset by one character in common mark files

[Bernhard Schuster]

Describe the bug

Off by one underline in common mark / markdown files.
Works fine in rust files.

To Reproduce
Steps to reproduce the behaviour:

1. Run 'cargo run -- check README.md'
2. See error

<snip>
    --> /media/supersonic1t/projects/cargo-spellcheck/README.md:169
     |
 169 | Run an instance of the [LanguageTool server i.e. as container](https://hub.docker.com/r/erikvl87/languagetool).
     |                          ^^^^^^^^^^^^
<snip>

Expected behavior
Precisely underline the mistake.

Please complete the following information:

• System: Fedora
• Obtained: git

Additional context
Add any other context about the problem here.

[Bernhard Schuster]

It only happens with the sequence of ```rust

` ```rust`

as present in README.md

[Bernhard Schuster]

Actually that is wrong,

<pre>🌡</pre>

triggers this reproducibly