title: nvim-lspconfig says Azure Pipelines boolean should be string
body: <p>I am running Neovim 0.5.1 with nvim-lspconfig cloned from their GitHub repository. Then I installed the YAML Language Server as described. I'm using Neovim to edit an Azure Pipeline and trying to set Parameters that are Booleans with defaults. However, the nvim-lsp seems to think it needs to be a string?</p>
  <p><a href="https://i.stack.imgur.com/OFM2X.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OFM2X.png" alt="nvim-lspconfig with azure pipeline parameter boolean" /></a></p>
  <p>Typically, I don't need to quote a boolean. This also seems to happen just for azure-pipelines.yaml and not things like Ansible, or other generic YAML. Would anyone know why, or how to correct this? Is it the nvim-lspconfig or something I'm doing wrong?</p>
  <ul>
  <li><a href="https://docs.microsoft.com/en-us/azure/devops/pipelines/yaml-schema?view=azure-devops&amp;tabs=schema%2Cparameter-schema#parameters" rel="nofollow noreferrer">Azure DevOps Pipeline YAML Schema - Parmaters</a></li>
  </ul>