Default to render code blocks w/out syntax highlighting instead of hard failure

[unmultimedio]

Creating a new issue from:

@Gerrit0 Just bumped into this issue, with another language. According to the docs:

By default, TypeDoc will produce an error if a code block specifies a language which is not present in the highlightLanguages array.

I wonder if there's a way to tell TypeDoc to not fail for unknown languages, but instead just render w/out highlight. I can open a new issue with this question if you want.

Originally posted by @unmultimedio in #2943