Code blocks should have the same background, font size and type

[EuropeanDeveloper]

Code blocks without defined language should have the same background, font size and font type as code blocks for the rest of languages. It is more uniform and looks better in markdowns with codes in multiple languages.

For example:

\```
  Something
\```

\```text
  Something
\```

\```batch
  rem Something
\```

\```html
  <!-- Something -->
\```

is rendered in Markdown Viewer 4.0 with GITHUB theme like this:

The same code formatted by GitHub:

Browser: Mozilla Firefox 95.0

[simov]

Again that's styled by Prism.js, but thanks for the feedback.

[simov]

That was fixed in Markdown Viewer v5, however, the Firefox release will come up later this year once they implement the support for Service Workers in manifest v3, so stay tuned for that.