Add documentation support on hover

[kitsonk]

This PR adds support for quick info documentation and tags, which is similar to the hover support provided by vscode.

An example for the following code:

/**
 * Some documentation
 * @pure non-standard tag
 * @deprecated which should be parsed
 */
function foo() {
	//
}

You get the following when hovering:

Resolves: microsoft/monaco-editor#203
Resolves: microsoft/monaco-editor#277

[msftclas]

@kitsonk,
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Thanks,
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[jrieken]

Don't think that we need this anymore. See microsoft/monaco-editor#203 (comment)

[kitsonk]

@jrieken I mistook the functionality requested in that issue, but I still think this PR is valid.

This provides support for documentation and decorators that aren't otherwise injested by the language services, just like vscode.

Given this code:

/**
 * Documentation goes here
 * @deprecated
 */
function foo() {
	//
}

This is an example of the hover provider in vscode:

This is an example of monaco-editor without this PR:

This is an example of monaco-editor with this PR:

[jrieken]

Ok, thanks.

[msftclas]

@kitsonk,
Thanks for having already signed the Contribution License Agreement. Your agreement was validated by Microsoft. We will now review your pull request.
Thanks,
Microsoft Pull Request Bot