Improve hover to include title, description and source schema link

[ssbarnea]

When hovering over an entry we can now see only the title from the schema and that may prove not enough for some schemas that also have a longer description field too.

Ideally it should look like:

{title}
{description}
Source: <a href='link-to-open-schema'>schema-filename.json</a>

I mention that both title and description may be missing and we should use whatever we find.

One example from XML schemas can be used as a nice implementation example

Also the auto-complete field functionality does not display the field title after the name, something that is highly desired for ansible module arguments. Without this the user would be forced to first auto-complete the entry and make use of hover after in order to understand the purpose of that option.

[evidolob]

@ssbarnea I create PR for hover.

As for completion, try to press ctrl + space twice you should see documentation popup:

[ssbarnea]

@evidolob Can you please give me some hints on how to test that PR? I always wondered how am I supposed to test yaml-language-server as the deliverable is not an extension, so I need to include it in a local build vscode-yaml but that was not clear to me.

[evidolob]

Sure, there doc how to run vscode-yaml with own LS https://github.com/redhat-developer/vscode-yaml/blob/main/CONTRIBUTING.md#developing-the-client-and-server-together