Support $schema property

[sevillal]

Support $schema property and enable dynamic schema registration for the files containing it.

[SiddhanthUnnithan]

• First we need to support the $schema property

• What do we need to do to support this tag?

• What is the best approach => start from scratch, build on top of what the RH team has already done, what happens after they add the support.

• Start with commenting on their issue and ask about progress / merge plans.

• Otherwise consider forking and publishing our own package.

[shsuman]

Following up with the RedHat team to know if they are gonna merge the PR.

redhat-developer/yaml-language-server#354

[shsuman]

Merged PR: https://msasg.visualstudio.com/OpenMind%20Studio/_git/OpenMindVSCode/pullrequest/2083544

and tracking conversation with RedHat in #960