CodeMirror OAS support

Plugin for text editor https://codemirror.net/ running in your browser that can fetch and parse your OpenAPI schema definition and provide auto-completion support (for large and complex JSON message payloads), error highlighting and access to schema documentation. It is capable of parsing megabytes of OpenAPI schema definition in a second and providing auto-completion support in milliseconds. The work is an MVP of a plugin with basic functionality made as part of a master thesis at ČVUT.