Allow "text" as a syntax highlighting language

[ericseppanen]

Bug Report

I frequently use this syntax to disable syntax highlighting. It works on other markdown implementations (e.g. github):

```text
some text here
```

The text language is the one I've seen recommended most frequently.

Zola only allows txt for this purpose. Would it be possible to allow text as well?

Environment

Zola version: 0.14.1

Expected Behavior

Using text syntax highlighting is disabled.

Current Behavior

When I run zola build I get many warnings of the form

Warning: Highlight language text not found in foo.md

[mwcz]

I could be wrong, but I think that change would need to be made in sublimehq/Packages/blob/master/Text/Plain text.tmLanguage.

[Keats]

You can probably add an alias in https://github.com/getzola/zola/blob/master/components/config/examples/generate_sublime.rs but tbh there's already txt so I'm inclined to not add text