Add support for library.json

Hi,

Would be glad to see support for [library.json](https://docs.platformio.org/en/latest/librarymanager/config.html), a unified and independent library manifest (any framework, any platform).

If some fields/data are missed in `library.json`, we can discuss and add them. Any proposals are welcome.

P.S: It should help with resolving of this issue https://github.com/arduino/Arduino/issues/6646

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See original discussion https://github.com/adafruit/DHT-sensor-library/pull/118

Start by reading the PlatformIO library.json configuration documentation and the linked Arduino issue and DHT-sensor-library pull request. Then determine how Arduino IDE 1.x currently handles library metadata and which manifest fields must be supported; done means library.json manifests work across the requested library-resolution flow.

Written by the indexing model from the issue text.