Language client: updated client capabilities with markdown support

src/source_language_protocol.cc

@@ -129,7 +129,7 @@ LanguageProtocol::Capabilities LanguageProtocol::Client::initialize(Source::Lang
   }
   // When using rust-analyzer instead of rls, remove: "initializationOptions":{"omitInitBuild":true}
   // Also remove: "workspace":{"didChangeConfiguration":{"dynamicRegistration":true},"didChangeWatchedFiles":{"dynamicRegistration":true} ?
-  write_request(nullptr, "initialize", "\"processId\":" + std::to_string(process_id) + R"(,"rootUri":")" + filesystem::get_uri_from_path(root_path) + R"(","capabilities":{"workspace":{"didChangeConfiguration":{"dynamicRegistration":true},"didChangeWatchedFiles":{"dynamicRegistration":true},"symbol":{"dynamicRegistration":true}},"textDocument":{"synchronization":{"dynamicRegistration":true,"didSave":true},"completion":{"dynamicRegistration":true,"completionItem":{"snippetSupport":true}},"hover":{"dynamicRegistration":true},"signatureHelp":{"dynamicRegistration":true},"definition":{"dynamicRegistration":true},"references":{"dynamicRegistration":true},"documentHighlight":{"dynamicRegistration":true},"documentSymbol":{"dynamicRegistration":true},"formatting":{"dynamicRegistration":true},"rangeFormatting":{"dynamicRegistration":true},"rename":{"dynamicRegistration":true}}},"initializationOptions":{"omitInitBuild":true},"trace":"off")", [this, &result_processed](const boost::property_tree::ptree &result, bool error) {
+  write_request(nullptr, "initialize", "\"processId\":" + std::to_string(process_id) + R"(,"rootUri":")" + filesystem::get_uri_from_path(root_path) + R"(","capabilities":{"workspace":{"didChangeConfiguration":{"dynamicRegistration":true},"didChangeWatchedFiles":{"dynamicRegistration":true},"symbol":{"dynamicRegistration":true}},"textDocument":{"synchronization":{"dynamicRegistration":true,"didSave":true},"completion":{"dynamicRegistration":true,"completionItem":{"snippetSupport":true,"documentationFormat":["markdown", "plaintext"]}},"hover":{"dynamicRegistration":true,"contentFormat": ["markdown", "plaintext"]},"signatureHelp":{"dynamicRegistration":true,"signatureInformation":{"documentationFormat":["markdown", "plaintext"]}},"definition":{"dynamicRegistration":true},"references":{"dynamicRegistration":true},"documentHighlight":{"dynamicRegistration":true},"documentSymbol":{"dynamicRegistration":true},"formatting":{"dynamicRegistration":true},"rangeFormatting":{"dynamicRegistration":true},"rename":{"dynamicRegistration":true}}},"initializationOptions":{"omitInitBuild":true},"trace":"off")", [this, &result_processed](const boost::property_tree::ptree &result, bool error) {
     if(!error) {
       auto capabilities_pt = result.find("capabilities");
       if(capabilities_pt != result.not_found()) {