Add diagnostics to language service using new property

[Chnapy]

Use of new LanguageService type allowing to access plugins diagnostics. This add was done for tsc-ls package: Chnapy/tsc-ls#1

export type LanguageServiceWithDiagnostics = tsl.LanguageService & {
  pluginsDiagnostics: Map<string, tsl.Diagnostic[]>;
};