Improve the project documentation and provide a better HowToGuide and simple code demo/test project for jsonrpc

[cmoulliard]

Proposition

Improve the project documentation and provide a better HowToGuide and simple code demo/test project for jsonrpc to let the users to better figure out what they should do

List of changes proposed

• Review the json rpc and getting started md guides
• Articulate the guide around a simple use case where the language server will by example search about a word in a dummy text packaged within the project and user will be able to query the language server to search about a text word
• Create a demo project similar to this one implementing the different pieces; LanguageServer, LanguageClient, etc
• Use JSON RPC annotations to create the user's request or get notification
• Merge the README with the jsonrpc guides
• Add/list some interesting blog posts

Remark: The code of this example project https://github.com/TypeFox/lsp4j-chat-app/blob/master/src/main/java/io/typefox/lsp4j/chat/server/ChatServerLauncher.java#L39C6-L39C54 is outdated and the following methid don't exist anymore launcher.startListening().thenRun(removeClient);

@akosyakov

[cmoulliard]

What it is not clear to me until now is if we must create a Server and Client class which implements Endpoint { and how to combine or not the @JsonNotification, @JsonRequest and @Jsonsegment ?
@akosyakov