VSCode's custom keyword support

[jdesrosiers]

VSCode has some custom keywords that it supports. We want to support these custom keywords as much as is reasonable to ease transition for people who want to move over.

If you want to work on implementing support for one of these keywords, the first step is the create a new issue specifically for that keyword and link it to this one.

https://github.com/microsoft/vscode-json-languageservice/blob/2ff90f8f5e8e2399c5f78c7f7bdee92a4774fbe8/src/jsonSchema.ts#L75-L90

	// VSCode extensions


	defaultSnippets?: { label?: string; description?: string; markdownDescription?: string; body?: any; bodyText?: string; }[]; // VSCode extension: body: a object that will be converted to a JSON string. bodyText: text with \t and \n
	errorMessage?: string; // VSCode extension
	patternErrorMessage?: string; // VSCode extension
	deprecationMessage?: string; // VSCode extension
	enumDescriptions?: string[]; // VSCode extension
	enumSortTexts?: string[]; // VSCode extension
	enumDetails?: string[]; // VSCode extension
	markdownEnumDescriptions?: string[]; // VSCode extension
	markdownDescription?: string; // VSCode extension
	doNotSuggest?: boolean; // VSCode extension
	suggestSortText?: string;  // VSCode extension
	allowComments?: boolean; // VSCode extension
	allowTrailingCommas?: boolean; // VSCode extension
	completionDetail?: string; // VSCode extension

[Suyog241005]

Hi @jdesrosiers! I’d like to take this on and work through supporting these custom keywords incrementally.

Per your instructions, I will break them down into separate, dedicated issues and PRs per keyword so they are easy to review and track.

I'll start by opening an issue for markdownDescription first (since it's widely used across schemas for hover tooltips), and then follow up with completion-related keywords (defaultSnippets, enumDescriptions, etc.).

[jdesrosiers]

@Suyog241005 You may only work on one of these at a time. Do not submit a PR before being assigned. You can not claim this entire task. I expect others to contribute some of these as well.

[Suyog241005]

@jdesrosiers Sorry about that, I got excited to work on this issue and opened these PRs too early.
I'll focus only on markdownDescription (#87) for now. Would you like me to move the deprecationMessage and enumDescriptions PR to draft or close it so that keyword is fully open for someone else?

[jdesrosiers]

@Suyog241005 Sorry, I closed the PRs before seeing your last message. Yes, we'll close them for now.