Add codemirror mode for nim

[stisa]

• I have read the Contributor Guide
• I have updated the changelogs/current_changelog.md file with some information about the change that I am making the appropriate file.
• I have validated or unit-tested the changes that I have made.
• I have run through the TEST_PLAN.md to ensure that my change does not break anything else.

This adds a codemirror mode for syntax highlighting of nim
If there's some other plugin mechanism in place to load modes for languages not supported by codemirror please let me now and I'll try to use that.

Screenshot:

[todo]

- Can you have imaginary longs?

nteract/packages/editor/src/mode/nim.js

Lines 421 to 426 in 480b353

	// TODO - Can you have imaginary longs?
	intLiteral = true;
	}
	// Zero by itself with no other piece of number.
	if (stream.match(/^0(?![\dx])/i)) {
	intLiteral = true;

---

This comment was generated by todo based on a TODO comment in 480b353 in #5269. cc @stisa.

[willingc]

Hi @stisa,

We would be happy to add support for nim but taking a different approach than this PR. This PR adds Go support and outlines our preferred approach.

We recommend that you create an external package likely using much of the code in this PR.

Thanks! Let us know if you have questions. cc/ @captainsafia

[stisa]

Hi! Thanks for the reply.
Makes sense, I'll have a look at doing that.

Basically I need to:

• create a npm package for the mode
• add the package to the editor's dependecies (here?)
• require that in index.tsx

Does that sound correct?

[willingc]

@captainsafia Please correct me if I'm wrong.

@stisa I don't think you need to add the package to the dependencies. Much like Rust or Go, you would require it in packages/editor/src/index.tsx

[stisa]

@stisa I don't think you need to add the package to the dependencies. Much like Rust or Go, you would require it in packages/editor/src/index.tsx

@willingc I'm pretty sure it's needed, to my understanding rust and go worked like that because they're already present in codemirror's package (here), they just weren't required by nteract. As my mode is external, a dependency is needed for npm to pull it from the registry.

(sorry if I'm wrong, I don't know much about javascript development)

[willingc]

Thanks @stisa. Your points make sense to me. @captainsafia thoughts?

[captainsafia]

Unfortunately, we will need to include it in the package.json since it is no bundled with the default set of syntax highlighters that CodeMirror provides.

I say "unfortunately" because this is one of those things that I'd like to avoid having as a dependency of the package and instead allow people to configure in the desktop app.

I don't have any ideas on how to make that possible now but I am open to hearing ideas from others!

[stisa]

Yeah I understand adding dependencies just to support a language isn't ideal.

One way to do it could be like with jupyter notebooks, where a special file kernel.js is loaded from the kernelspec folder, eg. in loadMode if no mode is found try looking for a <language>.mode.js in the kernelspec folder (or similar) that provides a register function, but I'm not sure how doable it would be with nteract's architecture.