Support for inline code

Quite often I want to write about a variable or function name (yes, "everday writing" for me). Sadly, I cannot style `someVariable` or `myMethod()` like here in GitHub. I usually resort to _emphasized_, but that takes that away for other use cases or makes it ambigious.

```
Code blocks do work,
but disrupt the text flow.
```

So, inline code would be awesome!

The issue names no file, test, or entry point. Start by locating Trix's existing inline-formatting behavior and its tests, then compare how emphasized text and code blocks are handled. Done means users can apply inline code to variable or function names without disrupting surrounding text, with the behavior covered by tests.

Written by the indexing model from the issue text.