[json] NPM package for vscode-json-languageserver not sync'd with VSCode releases

The NPM package for vscode-json-languageserver is not sync'd with VSCode release. It was not published for 5 months (mid-September), while the LS received several updates in VSCode source tree and releases. There are 2 issues: * In vscode, the vscode-json-languageserver module version is more or less unmaintained. The vscode-json-languageserver is treated as an internal module so version concerns are secondary. * When VSCode releases, no new release of vscode-json-languageserver seems to happen automatically. That makes the npm module more or less useless: we tried to adopt it in Wild Web Developer and got missing features, or unexpected older dependencies, conflicting with other LS we "extract" from VSCode. As a result, we move back to extracting this JSON Language Server from VSCode. I think it would be in the best interest of the LSP community if this language server were extracted from VSCode source tree as a standalone NPM module, with proper versioning and published to npm.js. Then consumers (VSCode, Wild Web Developer...) could just install this module with some guarantee of it being up-to-date. Same pattern could apply to other LS and debug adapters included in VSCode (HTML, CSS).