chore: note about maintenance mode and suggested other options

This library is not deprecated or archived. It still works fine and we are reviewing pull requests and make releases. The core maintainers just don't actively invest in new features.

README.md

@@ -2,7 +2,7 @@
 
 [![npm version](https://img.shields.io/npm/v/typescript-json-schema.svg)](https://www.npmjs.com/package/typescript-json-schema) ![Test](https://github.com/YousefED/typescript-json-schema/workflows/Test/badge.svg)
 
-Generate json-schemas from your Typescript sources.
+Generate json-schemas from your Typescript sources. This library is lightweight and more or less in maintenance mode. For a more complete JSON schema generator, take a look at [ts-json-schema-generator](https://github.com/vega/ts-json-schema-generator).
 
 ## Features